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Main Station is located at Dubbo (2830), 500kms north west of Sydney on the Central West Slopes and Plains of New South Wales and  supported by a mobile radio platform based on a 1974 VW Kombi Van allowing Ham operations when away from home. 























Photo above:  VK2BLC station embodying recycled radio systems and a wide variety of surplus and homebrew equipments that form a Ham station. Underlying this a strong technical interest in how things work and a hands-on opportunity to interact with the art.  The ham station was and continues to be a work in progress. 



1. Station equipments overveiw and photos.

2. Remote receiver site under construction describes current progress. This is a major homebrew project over long period as it involves infrastructure and large homebrew CES. 

3. History of the Collins AN/TRC-75 transceiver from inception  to war in vietnam an its subsequent disposal from defence and use in amatuer service by VK2BLC. 

3. Progressive monthly diary entries with reports of ham activities follow and are updated monthly.  Bold headings indicate homebrew activities which may have generic interest and wider applications.

For example

Harris RF-1030-02  HF Transmitter, assembly ( RF-1310, RF 110A  and RF-124) commissioning of system from equipment archive and repair of interlock problem. (31st July 2017) 

HP 8662A RF Signal Generator Restoration , details process followed to bring a E-scrap unit to serviceability with emphasis on powers supply repair methdology . (17th March 2017)

Harris R-2368-URR  RF-590A Receiver Modification,  improved SSB operation when receiver used with colocated transmitter or net operations with widely varying signal levels (26th December 2016)

Very usefull hint in the testing of faulty switch mode power supplys in powered up mode allowing troubleshooting of HP8662A and HP1660A and general SMPS power supplies   HP1660 repair ) (30th October 2016)

Tantalum problems in Collins HF80 (27/09/11)(13/07/08)(15/08/11), and accoustic noise quietening in RF-110A Harris based systems (17/10/08)(22/01/13),

Trouble shooting of Collins AN/PRC-47 HF radio set removed from long storage (26/01/16) 

Repair strategies for the Harris RF-1110A and the RF-1124 (05/06/12) .The construction of a 600kHZ channel spaced notching duplexer (18/10/12) . A digitally implemented STR-8212 HF receiver has been installed for direct comparison with the analogue Harris and Collins radios(17/11/13) .

Repair and troubleshooting Harris RF-1310 exciters (22/03/12)(22/01/13) .To reduce energy costs the Ham shack has been converted to homebrew 5KVA solar power system (17/02/14) . Considerable mechanical work was required to repair the VW Kombi radio platform in two cycles of failure, details are in the text.  

A repair methodology is detailed to help repair HP8640 RF signal generators to restore FM deviation and band display indications(30/09/15)

Homebrew 1 metre transmitting loop and NVIS field tests  ( 6th May 2006)  

Dates in brackets are ham diary locations.

Brief Australian army history of Collins AN/TRC-75 and some Harris RF-110A and RF-1110A amplifer background which forms the main equipments in use is mentioned.

All equipments are sourced from surplus or re-cycle. Usually are redundant, written off, unserviceable and or obsolete systems and components. Input costs can be low and the recent era equipments more readily modifiable to suit homebrew and conversions to amateur applications.



Main Transmitter one: Collins AN/TRC-75 28,000 channel synthesised transceiver, ( manufactured 1961), modified for quiet operation , as shown in photo below. 

These TRC-75's used by Australian Army in 1965 were removed from 109 inch long wheel base FFR (fitted for radio) landrovers )and sold as military surplus in 1978.

Electronics designed 1956 . 46 tubes,100 transistors, 162 diodes , 17 mechanical filters, 6 servo systems , fully automatic tuneing , 7 controls to operate. Final power amp tubes, three 4CX250R , weight 165 kGs. (363lbs) . 

Power requirement is   3 phase star ,  208Volt /115volt , 400Hz, 2500 watts. Operating from modern inverter. Standby input  is 35A @28 volts DC. 70A peak  at 400 watt SSB output . For maximum RF output CW key.  120 amps @28V DC in.

Hi end performance: 

Receiver: RX sensitivity 0.3 uV@12 db S+N/N at 28.5 Mhz , smaller then 1uV for any of 28,000 channels.  2.6Khz bandwidth,  Freq stability 0.1 PPM,  Dynamic range and blocking >100 db . Reciprical mixer noise - almost immune. Local permeability tuned oscillator phase noise , -130db/hz  at delta 10KHz from Fo. PTO Oscillator frequency range 2- 4 Mhz .Creates all  HF frequencys by mixing and multiplication. 

Transmitter: SSB, 1kw PEP ,  >40 db 3rd order  intermodulation.  Harmonic  2nd and above <-40 dbc,  Nonharmonic <-60dbc,  Total audio system distortion 1.4% (15 db audio compression) (1KHz) measured at test receiver. Supressed carrier rejection  >40db,  Hum and noise <-50db.  CW 1.2kw, FSK 0.7kw  rf output. Revised power ouputs in amatuer service. 

Inbuilt antenna coupler (used only as a line leveller) , max tune time 30 secs , average  12 secs. Amplifier tune time <3 seconds. Typical overall system tuneing 20 secs

The transceiver is remote controlled from operating desk. Associated reciver is  Harris RF-590.

Photo below shows:  the AN/TRC-75(  modified) transceiver . Note the remote facilities connector incorporated by Collins Alpha Corporation , Dallas for the Australian contract on RHS lower . This transceiver is remote controlled from desk area and fed transmitter audio. It is used as the primary transmitter in conjunction with the harris RF-590 search receiver . Receiver audio from this tranceiver is also available at operators position. A internal splitter splits the RX signal path at the input to the R-761/AN /ARC-58 input and fed to the operators desk main Harris receiver. This is necessary since the internal transmatch ( CU-749 coupler) also matches the antenna to the TRC-75 receiver .
























Photo below shows: The 28V 3 phase 208V 3KVA sine wave static inverter ( top RHS) used to power the AN/TRC-75 in the adjacent ham shack with its homebrew control and protection interface. The unit marked 107 below is the original mobile homebrew 2.5KVA 4 phase static converter control and environmental protection ( one filtered sine wave phase and three stepped wave phases) cabinent . The cabinet contains the original Collins PP/2352-URR inverter (1960) ( 38 switching devices)  ( used in AN/MRC-87) and is used here as a back-up supply. A LED cluster can be seen on the top LHS near the label 107 , these form the transistor test system and indicate any blown individual transistor fuses allowing the TRC 75 to operate on reduced power. A operators choice based on just how many devices have failed. This supply system  will be replaced with a AC mains driven frequency converter. A photo of the PP/2352-URR is at the bottom of this station biography.
























Photo below shows: The  TT-4C/T6 Kleinscmidt teletype unit manufactured by Smith Corona Marchant Inc originally used  with the Australian AN/TRC-75. The enabling of the TTY function has been a background task. The TRC-75 is fitted with a CV-786 converter. A  Harris RF-3466A  Data Modem is under repair to act as the in shack mirror for testing.  

























Photo below shows: Rear view of the AN/TRC-75 transceiver showing the AN/ARC-58 avionics airborne boxes assembled into a ground package. For servicing and maintenence strategies without a GRM-10 test bench, initially black boxes were  reversed from the cabinent, de-canned and re-connected to the CY2600 looms. A significant shelf was  provided behind the CY-26000act a service support bench. Blower airflow was found not critical for the R-761 as most service effort was expended on the receiver exciter. The T-730 troubleshooting is limited and needed engineering solutions to allow full testing. Adequate forced air flow and safety considerations had to be implemented.   A large number of test points are available on the R-761 and easily acessible , However component level troubleshooting will require module extenders. The 2848 coupler control itself can act  as a test bed and aids servicing and checkout of  the servo modules AM1525 . The CU-749 coupler can also easily set up to observe working.






















Standby Transmitter two: Harris RF-1130-02 transmitter system (manufactured 1986) ( RF-1310 exciter , RF-1110A linear amplifier, RF-1124 ) SMPS (switch mode  power supply) as shown below. The main features is the speed at which the system can be brought online. Around 30 secs if hurried and lower standby power consumption then the RF-110A system. This transmitter is remote controlled from operating desk. The RF-110A has been placed in archive .

TX spec: Solid state. 1kw PEP ssb, 1kw CW, 1kw average FSK.    217 lbs weight. Revised RF output values for ham service. Transmitt performance specs are similiar to the   RF -110A with exception of the 3rd order IMD which is not as high as the tube amp.The highest RF distortion occurs at the lowest powers and can be compensated with careful static bias adjustments to acheive minus 30 DBC.  The four PA modules  operate on 50VDC. The RF-1124 power supply is capable of 90 Amps DC peak output. Typical PA currents in service are 52Amps @ 50VDC for standard amplifier.  There is a 4KVA or more current transient inrush AC mains demand to initially charge the RF-1124 power supply HV supply. 

The RF-1110A Low pass output filter is divided into 9 bands over 2-30MHz. . The unit is modularised, has 12 removeable plug in assemblys.Has extensive VSWR protection and interlocks.  Can work satisfactarily into 4:1 VSWR loads . 

Power requirements 230Volt ac single phase  47-63Hz . AC input 3.5 KW /5.0KVA.

Photo below shows :  The Harris RF-1130-02 transmitter group. The solid state unit is the secondary station transmitter and is fed transmitt low level RF  and remote control signals from the ham shack operators desk.  The RF-1110A RF amplifier is shown with main drawer extended . A standard broadcast station audio architecture from microphone to two transmitters is copied and applied to transmitter via patch field. A two-tone test oscillator and additional RF-1310 exciter  allow stand alone local testing. 

































Photo below shows : The Harris RF-1110A RF unit rolled out for maintenence and can be operated in this position. The 5 RF amplifier modules slide out from the main chassis and require a D series combinational connectored extender cable if needed to be operated while troubleshooting. 



















VK2BLC ANTENNAS : Various antennas in use are Dipoles, tuned wires, one metre diameter small transmitting loop on pneumatic mast and reduced size 80 Metre delta with matching stubs.



03 November 2016: Work status as follows , Link racks version 2 under construction, Teknis voice/data modem yet to see succesful data message, System voltage determined ar 24 volts, Antenna array hitch points in trees yet find successful delivery system, NBN EMI regarded as reduced considerably , waiting on EMI survey to measure actual noise. (Traceable to CISPR). NBN EMI caused a 12 month halt  in construction .Work is now resuming.  Estimated completion December 2017.     

24th July 2016. No further work at the site this month and full evaluation of  interference levels and personalities is scheduled for September 2016. Traceable measurements and EMC mapping of NBN  equipments EMI  in conducted and radiated, levels from cables , power supplies, and interfaces will be made.  

7th  June 2016 .  Work at site is still on hold due to NBN EMI (ElectroMagnetic Interference) at the site. NBN have just attended the property and changed out their ( NTD) Network Terminal Device.  An engineer attended to supervise the work. there. There will be some time lag while the results are evaluated. 

There is no protection for HF noise interference to amatuer radio and in this case it is anticipated that once the AM broadcast interference (where there is statuary protection of intereference to broadcasting services) is cleared the HF will also clear. 

 While delayed with NBN solution pending , work is focussed elswhereA revised electronics  workshop with more space was constructed to allow more efficient fabrication of the remote receiver racks, previously metalwork fabrication was done weather permitting, another rack was fabricated. Both racks are now physically side by side to solve all the electronics packages integration issues, unify data transmission firmware and solve compatibility issues. Building the racks in isolation was not successful and two build standards were used. The new arrangement will see identical items in both racks. Redundancy also has been considered.

Photo below shows: Both ends of the remote receiver site link under construction in the purpose built electronics workshop to allow parallel development as mentioned .  






















At the site itself the NBN EMI ( electromagnetic interference )  issue has yet to be resolved.  The NBN visited the site and changed out the roof top microwave translator without any improvement. The problem is originating  from their NTD ( network termination device ).

Photo below shows: The surplus Stoddart field intensity meter AN/PRM-1A currently used to measure switching noise from the NBN NTD (network terminating device) . The instrument features an extensive range of  accessorys for measureing radiated (loops) and conducted signals and noise (clamp on probes) and confirming instrument calibration (coupling networks) useing calibrated RF signal generators. Quasi peak, gating and averaging options exist for pulse noise measurement 

The PRM-1A is shown on mains power and can be used on batteries. The unit on RHS is a battery powered audio amplifier. The unit is a precision tube unit built in the 1950s and was fitted with a battery eliminator for the 90 volt B battery. 

The FI meter  is normally used  for development  and proof of performance testing of VK2BLC HF  mobile, loop and fixed station antennas. 
























31st  December 2015 The NBN corp have not sent anyone to the site to assess the interference caused by their April 2015 installation of the NBN phone and internet service. Reported three times. Broadband radiated RF noise is up to 26mV peak (in worst case frequency slots in range 500 to 1.6MHz measured 1.5 metres from NTD  ). Radiation is from system boxes, interconnecting cables and mains power leads through the broadcast band and 2mV average on HF bands 80 and  40 metres. There is also significant noise injection into the common mode (house earth and nuetral conductors) . If the broadcast band interference is cured HF bands will follow automatically.

Under construction to solve high noise levels now at home QTH in the town expected completion 2015 , Rohde &Schwarz 400 series link equipments , Teknis Adelaide voice data modems , Homebrew 2 metre log spaced yaggis for 15 km path. Rockwell Collins HF-8050A HF receiver, HF-8091 remote control , AEA 632E broadband HF full sized travelling wave broadband dipole array for receiving .Cleared tree arpeture 43 metres.Equipment racks with supervisory telemetry and control. Path tests have shown feasible despite a number of knife edge transitions. A very quick test has shown signal levels will be sufficient and correlates with design predictions.

Photo below shows : Ham station homebrew remote receiver site link terminal under development . From top to bottom , Remote monitor /control panel , Test access patch panel , Voice data/ telemetry modem, Rockwell Collins HF receiver HF-8050A, Fan tray, Rhode and Schwarz 400 series 2 metre VHF link TX/RX, Order wire shelf, Codan voice identification messages playback unit, 24/48Volt power supplys, DC /AC rack power switching and supervisory telemetry pickoffs and control panel under construction.  































Photo below shows the benefit of adding small work platforms to the top of these narrow triangular towers as considerable time is spent there for different tasks . The 2 metre link antenna is end on to photo direction.( Photographer: Ron Swindley VK2DDQ Oct 2014)


































Remote receiver site update June 2015.  The NBN ( National Broadband Network )has been recently rolled out to rural areas and switched on . The EMI caused by the NBN equipment is so severe it will be  neccesary to have this out of left field problem solved before the site can be commissioned as a remote HF receiver site.  Broadband RF spectrum noise in HF bands lies in range of 200uV and up to 2mV ( average) in spot rf frequency narrow band windows. Effect on AM broadcast band reception is severe and this should lead to a fix .

Remote receiver site update December 2104. Work continues on remote receiver site: A number of related threads are in  process as parallel tasks,  The outdoor cabinet for shack duplexer link terminal completed and commissioned.Photos below

Antenna transmission lines and groundworks completed - All trenches filled and levelled , Photo below .

Number of termination pedastals where cables loop through or tap offs possible  installed , AC screened cable 240 volts mains supply to antenna array area and GPO raiser completed.   Antenna array mounting design completed to stabilise receiving array as trees move and from breakage, 1.5 metres of counterweights movement allowed , 8kg increments useing 30 by 30cm (12 inches)  useing pavers drilled with centre holes .

Photo below shows: completed cables right of way. Receiving array feeder termination pedastal in foreground























No solution as yet to rig steel antenna attachment ropes into 15 metre high tree forks. Antenna  termination pedastal completed and installed .LDF-450 heliax is direct buried to provide lightning protection along with coaxial gas arrestor to control internal coax centre conductor to shield voltages.

Photo below shows: Antenna termination pedastal during installation, (RHS) as well as 240 volt  equipments and maintenence supply GPO riser (LHS).Ground will be allowed to settle before cosmetic finishing touches .






















Link terminals rack equipments fabrication in progess, remote power switching and supervision rack boxes being built, These 19 inch 3RU units will contain build out to full current control capability from voice modem low current signals . They receive and process alarm data and condition it for receiving and sending by 16 channel telemetry .

Photo below shows: Control supervision and DC power distribution  rack interface under construction prior to lettering and wiring.Control currents received from VHF radio telemetry voice data modem activate high current relays of both AC and DC. Feedback signals are generated in this signal breakout  unit and sent back to the control station to indicate requested conditions have been acheived. Control actions and control success monitoring is echoed on the front panel . The relay panels were recycled from a similar control system and rewired to purpose.

























October 2014 . Antenna area and transmission line route cleared of scrub. Trenching complete. Waiting to complete the burial  of the LDF-450 hardline, flexible tails fabrication and installation antenna termination pedastal. Road crossing right of way completed . A powers supply and control cable has also been added to the trench . Waiting on succesful method to hang pulley assemblys from the elevated tree forks.


The number of equipments types in use is restricted or limited to associated system components of similiar series. Allows expertise to be developed to a specialised level. Also minimises quantity of repair parts and documentation needed to maintain systems in use. 

The electronic sophistication of recent defence surplus equipments highlights the need to be autonomous in  modifying, evaluating performance, trouble shooting  and increasing choices and success of  utilising these equipments calls for the development  good basic test and measurement skills . Current regulatory  issues of spectral purity of transmissions, frequency stability, Peak power measurement call for test gear on the shacks workbench. 

The continued use of tubed equipments requires regular testing to verify performance 

Fundemental shack test equipment is grouped and maintained. Updated 5th May 2017. The last 12 months was spent recovering e-scrap instruments to improve  the shacks  test equipment resources.  Multiple RF signal generators  HP8640B replaced by HP8643A , HP8642A and HP8662B  to reduce testing time of RX Blocking, Intermodulation distortion, 3rd order intercept, dynamic range, reciprocal mixing.  Frequency counter HP 5345A, Frequency standard HP 5065A, Audio and baseband Wandell and Goltermann PSM19 RF and audio mV and PS 19 signal source, RF power Bird 4386, Spectrum analyser HP141T series, Audio distortion meter AWA 242, Tektronix oscilloscope 2246, sine adder signal to noise meter, two tone oscillator and Master instruments standard VU meter. (for dynamic observations of transmitted audio). AVO 8 Multimeter, HP4815A Vector impedance Meter, HP8505A vector network analyser replaced by HP8753A with modified HP8503A S parameters test set .HP435B RF power meter, 30db high power attenuators, Fluke 26 DVM.

July 2016 onwards an effort is being made to upgrade HP test equipment to a later generation and add additional analysis capability in areas of pulse and digital signals. This upgrade has gathered pace and the basic list above will have more modern HP instruments for 2017. The  homebrew diary contains some references to these in process of being made serviceable.  

Basic Quality System is utilised. Calibration ,Safety, and Management of radio support items is organised to help support station. An effort is made to be resourced and repair capable to component level of all hamshack equipments in use.

Calibration of test equipment is by comparison of measurement by two or more instruments of same parameter 12 monthly and labelled. The parameters of most interest are (DC volts), RF frequency ( HZ ) and RF power( AC volts average and peak) . The rubidium frequency standard drift is accepted over time as required transmitter accuracy is only 0.1 part per millon.

Safety inspections of masts, guys systems, batteries environment and 400Hz power systems connectors are made 6 monthly. Ongoing awareness is maintained of Radiation Hazards, High voltage, Extreme DC fault currents, hazards like BEO ( beryllium oxide) (discarded BEO parts are in safekeeping) and working at heights. Fundemental safety equipment is maintained.

Radio Support, Repair spare parts and assemblies are managed , tagged with status and grouped in storage by radio type in one location. Extensive use is made of clear pallet wrap to protect items in long storage. Documents and test fixtures in use are kept close to systems in operation and remainder not in use are stored remotely.

Antenna changeover system has a transfer relay and two dummy loads , the unused transmitter is always connected to a load.

Most Collins equipments operate on 400 hz and 28 volt DC , It is necessary to generate 3KVA of 400 Hz and 120 A at 28volt DC to power the military surplus equipments from 50 HZ mains or solar supplies .

Power supplies and Systems : Primary 240 volt mains power system is a 5KVA stand alone battery backed solar system. This system then uses high current  AC to DC 28 V regulated float power supplies to drive a battery backed 3KVA 400hz 208V three phase static inverter to power the Collins high frequency AC equipment .

The overall system goes DC to AC then AC to DC then DC to AC . Shack ancilliary systems such as lighting , heating , cooling, and test gear , HF receivers use solar generated 240 volt 50HZ power directly. In September 2017 a mains single phase solid state sine wave frequency changer was being constructed to supply the AN/TRC-75 directly from 240 volt solar power and by pass the extensive AC to DC to Batterys to AC system improving efficiency and feeding the shack 400Hz distribution system.  

Secondary power of 208V 4 wire 3 phase 400HZ 3KVA is generated by a static inverter operating off a 28 volts DC system. The associated ac 400 hz switchboards and power supply distribution is by cannon connector based systems. The static inverter is battery backed by 660 amp hour bank of pure lead yuasa cells and DC system is floated on mains input constant potential 50 ampere DC 28volt power supply .

24 volt emergency transmitter and general control and supervisory power is also from the two by 330 AH 2 Volt Yuasu cells 24 volt battery banks each with 100Amp HRC protection . AN/TRC75 is backed up by PP-2352 208V 2KVA 3 phase 28V DC inverter , Shack AC system is fed by 5KVA , 240 volt ac inverter with input voltage of 48 volt DC ,200AH Battery bank of Hawker Energy SBS-110 cells. Charged by 3,000 watt solar panel array..

Shack configuration operating desk below : Wrap around operating area ergonomically organised, Single microphone and associated audio modules drives the two main remotely positioned transmitter via a patch panel . A emergency 28 volt Datron transceiver is used if no AC power available. Photo below : Shows concept of wrap around , additional microphone is part of emergency backup transceiver. LHS lower is main station RF-590 RX, HF Multicoupler. LHS mid upper is shack systems control , LHS upper is the emergency 24 v DC operated Transworld T-1000/TW-100 HF transceiver system, LHS middle under tape recorder is the Transmitting magnetic loop controller RHS lower is AN/TRC-75 remote control ,above is Harris RF-1310 exciter controlling remote RF-1110A amp , R-2368/URR matching RX, above is Rockwell collins HF-8090 remote control for distant receiver site HF-8050A, RHS top is HF-8014A and HF-8054A HF-80 components currently not in use.














































Photo above shows: VK2BLC collage 2006, above that is VK2BLC collage 2008 , above that VK2BLC shack 2012

Photo below: shows sample of VK2BLC real time logbook for part of May and June 2015.

















Photo below shows : Homebrew shack 5KVA solar system electronics area 


































Photo above shows homebrew shack 5KVA solar power system under development. DC battery voltage is 48 volts 220AH, nominal MPPT regulator system is 2KW (top LHS), is fed by 3,000 peak watts of Photovoltaic cells. On test the PV panels yeild a maximum of 2.4KW. The difference is explained in that panel outputs are altitude and installation sensitive. A additional factor is the matching of the actual PV panels optimum power point to the chosen system voltage. There should be attempt at convergence. A EMI filter (top RHS) is fitted to reduce PV panel radiation of MPPT regulators and inverter EMI in broadcast band.


Retrospective Photo below shows: Original AN/TRC-75 (circa 1961) modified VK2BLC Ham shack installation as it was in 1979. Internal vaneaxial blowers removed and remote air supplied at 4.5 inches water gauge . Coaxial cable connection to cabinet.replaces high impedance whip insulator. Internal coupler acts as transmatch. Homebrew 1.5 KVA 400HZ static frequency changer RHS lower powering system via original power board. Mid RHS lower photo .

Current installation in 2017 is at top of this bio. Same radio has been in use since 1978.













































Photo: VK2BLC remote receiver site 2011, Rigging works, signal testing , 86 foot VHF link antenna tower under construction


Photo: Remote receiver site 86 foot tower under installation and connection to 6 by 2 tonne concrete anchor foundations.
























Photo: completed remote HF receiver VHF link tower 2013.
























Photo: Completed antenna installation 2013, homebrew 2 metre yaggi lower left , homebrew 18 element UHF yaggi Tv antenna, top left, off shelf 20 element broadband wireless yaggi antenna top right , 10 element homebrew backup broadband wireless yaggi, tower electron discharge type lightning arrestor prototype.



The kombi is favoured because of its immunity to high level RF fields , rear engine placement, ease of suppressing vehicle electrical noise, walk through cabin, all metal body with little use of plastic trim panels, compact size and ease of drilling cable access holes anywhere they are needed. Has four  electrical systems. 240 volt 50hz, 14 volt and 28 volt DC , 115/208 volt 400Hz.

Photo below shows: Portable operation at Matilda bay in Perth, Western Australia. The tapered 32 foot fibreglass whip (AT-1011) is very close to a quarter wave at 40 metres and the most used antenna. 
























The VW Kombi van is set up as generic radio platform and operating area allowing different equipments and configurations can be set up and demounted with ease.

A  Transworld Datron TW100 transceiver and  Transworld T-1000 28 volt solid state linear amplifier set to 400 watts forms basic permanent transceiver. Other systems types are added as required.

Harris CU-2397/G 500 watt high speed antenna coupler and a AT-1011 30 ft (10 metre) whip antenna for stationary operations and 15 foot sections semi bent over vehicle are used for mobile operations.

CSA "longshot "travelling wave broadband multi configurational antenna kit used for quick set up as base station.Configurations are broadband inverted V, broadband delta, terminated open V (500 ft legs) , broadband dipole. Extensive use is made of carrabenas to quickly fabricate antenna sections into the different working configurations. Flexible metalized multi stranded kevlar forms radiating elements.

The Miller AT2500 antenna tuner is used if high power is ever required . .

Separate 24 volt electrical system comprising sealed sintered plate aircraft 35AH low impedence battery, Neihoff 30 ampere 28 volt vehicle alternator with solar panel supplement.

Has demountable Harris RF-1110A amplifier  , Operating desk and supporting equipments together with camping kit and supporting gen sets back up the Kombi flexibility. The harris RF RF-1110A was retired in 2015 and is being replaced by a Collins 718U-5 lightweight communications system. 

See vehicle related photos near February 2013 and June 2012 and other places.

I purchased the Kombi in 1974 and in 1979 a Collins AN/TRC-75 was installed as a mobile rig and towed a 5KVA 400 Hz desisel gen-set.( the original Bucknell Gen-Set used as part of the 75's  CES) (Complete  Equipment Schedule)

Due to space limitations in the Kombi the TRC-75 transceiver was later removed and fitted to a quarter ton defence surplus Haflinger trailer and powered by the PP-2352 collins inverter sourced from the US  AN-MRC-87 jeep mounted system.

A  nickel cadmium battery bank was integrated into the trailer and towbar mounted surplus DC-Gen Set acted as a charger .The 651-E1 duplex receiever and remote control unit was used inside the Kombi while mobile to operate the trailer mounted 75 set.

The box kites, hydrogen balloons and braided antenna wire from the readily available surplus gibson girl distress transmitter kits were used frequently to supplement the AT-1011 whip antennas .  

In 1987 the kombi was fitted up with a AN/ARC-102 HF system which had as it primary components the Collins 618T-3 and 490T-1A antenna coupler. 


The AN/TRC-75 (circa 1961) is a 1KW HF SSB , 28000 channel synthesised autotune transceiver . Collins radio , Cedar Rapids, Uses only one crystal to control the accuracy of any channel. The tubes receiver has a noise floor of -127 DBM measured in 3khz bandwidth. It is single cabinent integration of the airborne AN/ARC-58 ( designed 1956) used during the cold war in B-52 aircraft from 1958 for reliable long distance HF communications. The ARC-58 was a product of the project "Birdcall" with General Curtis Lemay as the driving force as the head of SAC and was himself a ham K0GRL.

The AN/TRC-75 (modified) radio and a duplex receiver 651E-1 with extensive audio facilitys control panel supplied under australian contract were designated as Duplex system VC-103A. The VC-103A comprised a modified AN/TRC-75 transceiver , A Duplex reciever 651E-1 in cabinent with audio control panel and lines interface, power was supplied from a static frequency converter 770A-1solid state , and a system source voltage of up to 250 volts 60/50 Hz ac. A additional AT-1011 antenna system compising 8 whip sections , base section and antenna lead-in was used as the 30 feet vertical duplex receiver antenna.

The Australian army fitted these into a long wheel base landrover and supplemented it with an operating desk , CW key, TTY (Kleinsmiddt), radio teletype converters , ISB (independent sideband) line interfaces patch panel and hybrids . A separate AT-1011 antenna system was located a 100 ft away on a ground spike.

Photo below : Shows VRC-103A system installed in 3/4 ton series 2, 109 inch wheelbase land Rover to become a FFR AN/TRC-75, 1966. Acknowledge photo source as publication 7610-66-018-8994 user handbook , army .
































Photo below shows: a oblique view of the FFR AN/TRC-75 vehicle installation.






















By the time this publication was printed , it detailed the CES of the FFR AN/TRC-75 including the Bucknell 400 Hz onan deisel generator fitted into a 1/2 ton 2 wheeled Aust No 5 cargo trailer to become a self contained installation.


Deployed to Vietnam theatre for the first time in May 1965 The Collins FFR AN/TRC-75  sucessfully opened radio circuit communications from Tan Son Nhut near Saigon to Watsonia Melbourne Australia.

The  first contact was made on the 30 May 1965 at 0105Z and subequently going to keyboard for 4 hours a day as Australia's sole rear link from Vietnam to Australia. The initial FFR-AN/TRC-75 was located at Tan Son Nhut and connected to Cholon Signal Centre in Saigon HQ by 15 kms of D10 cable. This followed close on to the work carried out by the reconaissance and advance partys under command of 709 Troop Captain R Twiss from the 26th May 1965 onwards .  Two more FFR-AN/TRC-75 were delivered by Hercules C-130 and by the 26th of June 1965 three FFR-AN/TRC-75 were serviceable and operating in theatre. Two at Ton Sun Nhut and one at Bien Hoa. 

Power requirements were 400Hz , 2500 VA 3 phase 208V. Initially two  Bucknel 5KVA  Onan 2 cylinder (2000RPM ) diesel generator sets were provided with each TRC-75. They quickly failed on mass due to overheat or other engine cutoff initiators, leaking main oil seals, blown head gaskets, and transistor failures in the  regulator.

The australian Bucknel deisel generator sets were unreliable from the start and received considerable initial communications to Australia for parts support. The US forces came to the rescue and loaned a USAF 400Hz EMU-12 gas turbine unit pictured. Despite the EMU-12E  being rated  rated at 20KVA 3 phase it was a very compact trailer mounted unit similiar to the size of the Aust No. 5  Bucknell cargo trailer combination. 

Photo below shows: the USAF EMU-12E 20KW 3 phase 400HZ gas turbine generator set loaned to the Australians to power the FFR TRC-75's at Tan Son Nhut and solve a severe reliability problem  with Bucknell deisel generator sets to sustain power to rear link communications operations to Australia in the period of June 1965 . Note the absolute compactness of this type of power plant more suited to 24/7 powering. The turbine engine is a Garrett Air Research GTP 30-67, 40 BHP, 52,870 RPM . Reliability came at a higher fuel consumption  of 30 litres of JP-4 aviation kerosene a hour ( 7.5 us gals)  compared to the distillate consumption of the Bucknell of around 2 litres and hour  ( 0.5 us gal).  Photo by Ron Preddice (1965) 709 signal troop, Royal Australian Corps of Signals album. 




















More technical descriptions of the Collins AN/TRC-75 towards the bottom of this bio. Vietnam theatre information acknowledged from "Pronto in South Vietnam 1962-1972" publication. A document to HQ from SVN dated 7 March 1967 for period August 1966 to February 1967 indicated 9 AN/TRC75's were held in the equipment pool, of these only 3 were serviceable. For the Bucknell 400 HZ gen sets, of 18 held in the pool , only 5 were serviceable. Other information is taken from "Australian War Museum  Series AW M95 Australian Army Commanders Vietnam Diarys , Signal Units, 709 Signal Troop , 26th May to 30 th June 1965".

Photo below shows: Corporal Rex Gable at 1RAR HQ Bien Hoa, South Vietnam,  September 1965 operating CW on active duty operating a FFR Collins AN/TRC-75 and accompanying Duplex Receiver 651E-1. VC-103A system.  Photo is acknowledged from Australian War Museum collection  AWM DNE/65/0340/VN. The morse key in use is not the one pictured in the CES of the VC-103. The Kleinscmidt Teletype and TTH-5 TTY converter is also absent from this FFR AN-TRC75 Land Rover.
































Not so well known was the initial delivery of the VC-103A was powered by a solid state 120/220 volt 50HZ to 400 Hz static frequency changer using SCR's. On first use in Australia in a mobile role USA based engineers were disbelieving that the RF interference from the 400Hz power supplies rendered the vehicular radio system useless. This was quickly followed by a spate of failures of the power supplies themselves. This was due to the insufficient insulation voltage between the SCR's and the chassis since the Australians used 230 volts and not 115volts and the auto stepdown transformer was non isolating. The aluminium oxide insulating heat transfer washers were not up to the task. 

Immeidiately the army called on Collins under warranty for solution and a 5KVA deisel 400Hz gen set was designed by the Bucknell company in conjuction with the Directorate of Signals and Army design Establishment . Prototypes were supplied and evaluated and a further 30 units incorporating the changes were supplied . The whole development process slowed the issue of equipment to units.



The original collins VC-103A systems were built in 1961 and the systems were put together by Alpha Corporation in Dallas. The cost of the VC-103A systems in 1961 was around 125,000 usd each to Australian government including spares, support and later factory training. At that time a average house in australian regional suburb cost around 4,000 australian pounds (8000 usd).

The Contract is estimated to be worth around 3.75 million dollars usd. Since there was 30 systems ordered in very late 50's or very early 1960's.

The Collins AN/TRC75's were issued to units between 1963 and 1964 and entered the vietnam war theatre in 1965. Whatever the teething problems the Collins AN/TRC-75 was technically far superior to any existing australian army HF vehicular mobile equipments of that time. The AN/TRC75 was superceded by the General Dynamics AN/GRC-106 in the following near years.

The Australian Army disposed of these VC-103A systems including CES to military surplus at St Marys, Sydney 1978 for 70 aud each for first 12 systems. The remaining 18 systems reached an average of 140 aud. They had a inservice life of just 15 years.



In the early 80's a small group of amatuers in Australia were successfull in getting their TRC75's on air and operating these weekly over a 18 month period on 7040 KHz  . Principly they were VK2BIM, (Lindsay Adams )  VK2BJI ( Dave Kent ) , VK3AAR ( Rod Reynolds ) VK7KW. VK3AAR and VK2BIM provided the engineering and technical input to solve powering and repair issues.  Several other calls were keen and did manage a few contacts. In mid 2000,s VK4VN (Steve Darveniza) succesfully assembled a  system and brought his AN/TRC-75 on air useing the PP-2352 static inverter. 



Following the purchase of the Collins AN/TRC-75 equipments as military surplus in early 1978, the radios performance  and  potential operational versatility was exploited in ham service. It became VK2BLC's only radio replaceing at that time radio shack systems and is still in use as primary radio 2016 . It was used, as main shack transceiver, field day demonstrator, on mobile weekends trips, and over the intervening years supplemented a number of WPX  contests as in photos below. When deployed for 48/7 WPX contests the 75 had never failed in the field. The principle benefit of maintaining and repairing this SSB radio set was its instructional, communications practices  of both deployment and operational and electronic skills legacy. 


Photo below shows: The  VK2BLC AN/TRC-75 portable at Tullamore 1980, NSW  standalone configured for 40 metres with homebrew HF discone . 5KVA Bucknell diesel generator set in foreground. The WPX contest multi  multi operator station hosted by Peter Ferrari VK2BXQ  generated 7.88 million points  for 5,214 QSO's. 























Photo below shows: VK2BLC as single operator, WPX contest 40metres , Collins AN/TRC-75 in VW Kombi

























Photo below shows: Rear of the 40 metre VW Kombi WPX station with VK2BLC and  Peter Ferrari VK2BXQ. 

























Photo below shows:  The VK2BLC  AN/TRC-75  portable at Tullamore, NSW  in 1981 configured for 21 MHz with 10 metre tower and 4 element beam.  The WPX contest hosted by  Ron Swindley VK2DDQ  as a multi multi operator  station, Group produced 6,416,627points  for 4,081 QSO,s. A 300 meter (1000 foot) landline connected  the AN/TRC-75 to the remote radio control console in the homestead and was operated by a rotation of operators.  













Photo below shows: Inside Kombi view and the toll on operators 24/7 operations during WPX with  Collins TRC75 on 21.265 Mhz ( 15 metres).No faults occurred in the TRC-75 for the 48 hours of continous operation. 





















Photo below shows: VK2BLC refuelling the Bucknell 5KVA diesel 400HZ alternator set during WPX 24/7 operations of the AN/TRC-75. Tullamore early 80's. The generator set would  run  12 hours on 20 litres of fuel. Ran non stop for 48 hours , was refuelled without stopping.





















Photo below  shows: The VW Kombi VK2BLC mobile station with towed 5KVA  power source , Burrendong dam, Wellington, NSW, mid 1980's. Two whip antennas , the AT/1011 32 foot when stationary ( direct high impedance feed ) and the high power helical on the front of the vehicle. ( 50 ohm feed) 


















Photo below shows: The Collins AN/TRC-75  and the additional Collins duplex receiver in the foreground along with operating desk






















Photo below shows: The 5KVA 400Hz Bucknell deisel genset used to power the AN/TRC-75 and normally operated while mobile. 























Photo below shows: The Collins AN/TRC-75 during demounting in late 80's from Kombi and being reconfigured to operate self contained as  a 1/4 ton Haflinger box trailer installation . Nickel cadmium batterys  were used in conjunction with  the US  standard PP2352  400Hz inverter ( pictured right hand side foreground in homebrew enclosure) . A 30 amp 28 volt army surplus petrol generator was used to charge batterys.  




















Photo below shows: Mounting of the Collins AN/TRC-75 HF radio set on the haflinger box trailer during construction
























Photo below shows: VK2BLC near Nyngan, NSW,1989  with the re-configured  box trailer Collins AN/TRC-75 system. 






















The RF-1110A is the solid state replacement for the RF110A tube amplifier. Shares the same physical dimensions and system interfaces. Performance is similiar,and system is  lighter in weight.  The 200lb RF-124 is replaced by the 88lb RF-1124. The amplifier is heavier so tends to equalise out. Noticeable differences in operation is considerable is it is quieter without the 400 hz extra fast fan of the RF-110A . The blower is normally stopped, starting occasionaly. The amp just like the RF-110A features roll out chasssis, fully modular and ease of servicing while unit is running. The configuration is a dual redundant power amp and power supply one. Combines four 300 watt RF modules operating on 50 volt DC .The high power LPF uses block ceramic capacitors.  The RF-1110A is full compatible pin for pin with the RF-1310 exciter.  


The RF-110A is a component part of the RF-130-02 , a rack mounted autotuned HF ISB system manufactured by Harris in Rochester NY. It is the modern descendant of the Navy URT-23B (1962) . Its common component is the RF-110A linear amplifier or very similiar to the AM-3924B. This amplifier is unique in its design . Equipped with a pair of Eimac 4CX1500B tubes driven by a pair of 6122 tubes. It can be operated seamlessly and reliably over a wide range of of output powers. Some naval ships operate these amps at 500 watts PEP well below the amplifiers actual capability.

The RF-110A uses a broadband PA tuning network dividing the HF band into 2MHz slots. It could accept several exciters at once within a slot. For other slots the tuning time amounts to 3 secs maximum . Its band selection tracks its associated exciter RF-1310 . A microprocessor based unit with considerable embedded software to enable extensive features . The major pro of this system is it can be troubleshot and serviced without any special jigs or test equipments and tools . The RF-1310 has a signal generator mode for use as a controlled signal source and BITE diagnostics of itself. This system may be the last of the species from surplus of systems that feature traditional ham friendliness . Photos of the system are further down the page.


11th January 2018: VK2BLC has reached file size limit and biography is suspended while applying for increase.

21st December 2017, HP 8643A, HP8656A, RF signal generators were recovered from E-scrap , attention paid to cosmetic recovery process then repaired for shack use. 

 Photo below  shows : The HP 8656A signal generator set up to locate high phase noise cause in low frequency loop oscillator . The CRO is monitoring the 50Mhz reference and the HP 89410A VSA  ( vector signal analyser) on RHS is displaying close in noise to carrier  (10Mhz +/- 250Hz), the 50Hz hum spurrs are distinctly visable. This indicated lack of filtering on VCO  control loop varicap supply. Spurii level was -30dbc.



















Photo below shows: The RF output waveform after instrument repair at 10Mhz +/-5KHz with close in hum artifacts at -70DBc. A marked improvement in spectral purity can be seen 

























Photo below shows : The HP 8656A SG under repair with the noisy (VCO front RHS under test) .  A CRO was used to measure ripple on VCO loop varicap supply and faulty axial 500uF electrolytic electronic choke stage was found. Brown capacitor front centre, LHS front edge of VCO cage.























Hewlett Packard 8643A  RF Signal generator:  sourced from E-scrap was cleaned and missing cabinent parts fitted. The self faultfinding diagnostics were run and during process stops and declares the fault code in order of discovery.The first was "+2,100,1nn"  Fast VCO . The + indicating a definate failure. The complete module was replaced, and process rerun.  The next fault code "+ 3,020" Frac -N module was replaced and MLD ( module level diagnostic program rerun and successfully displayed" 0". The MLD is initiated by selecting  a switch inside intrument. The HP 8643A, 8643B, 8644A ,8644B  assembly level service manual was followed.

Photo below shows:  The HP 8643A SG under repair for failed power supply 4 hours into  burn in testing after previous work.  The  SG was set for 240 volt mains operation after spending a lifetime on 115 volts.  























Photo below shows: The HP8643A SG rear power supply area with faulty Power Supply module RHS























Photo below shows:  Failed PMR 209 series mains rated metallised paper capacitor (front RHS).Usually highly reliable. The failed cap gave of a very distinctive smell that identifies type.    
























27th  November 2017: Collins 618T-3B HF ,  Redarc BCDC 1240-LV RF Noise Supression, tasks completed this month was to recover a Collins 618T-3B  radio archived in 2000 and work to commission a 4 drive vehicle as SSB radio platform. In that process it was necessary to further quieten the  fitted 1240-LV battery charger MPPT solar regulator. 

The late model (1972) Collins 618T-3B was removed from storage and powered up with its test bench items. The dash 3B differs considerably from previous dash 3 builds as seen in photos below. 

Initially after switch on the radio was no go.The dual D series connector interface to the translator was serviced for misalignment as the autopositioner was observed not to operate on 100Khz digit inputs. The receiver improved dramatically by itself over a 15 minute period to normal sensitivities ( 0.3uV).  The TX was tested over its 28 MHz band slots ( checks translator turret alignments) in AM mode and yielded 125 watts RMS with no output on 2 bands. Fault finding traced fault to the PA module. Carefull inspection under operation and  physical inspection indicated a faulty mica capacitor on pie section output. PA module current was at maximum, servo ran to maximum limit and did not acheive a PA current dip ( view at front panel meter) , RF output watts was zero. 


Photo below shows:  The fundementals of the  618T test bench, from left to right. Battery operated audio amplifier , Carbon capsuled avionics microphone ( not visable), The 67P-1 test harness fitted with 714E-4 1Khz stepped control. Frequencies from the 618T-3B were seen to be 1 khz in error when correct 714E-6 control was not used .Centre are the PA and translator modules removed from 618T radio chassis RHS.In front are some items from the 678Y-1 maintenence kit. The chain puller for the PA module , The 4CX 250F tube puller ( like V shaped flat spring with strategic indentations to catch on tube fin assembly), some alignment tools, and the usefull 7 and 9 pin tube extensions with test points used for translator fault finding.   



















Photo below shows: The 618T-3B modules that differ from the 618T-3. From RHS to LHS the control converter provides the 100hz steps , the divider stabiliser top centre which has become the replacement VFO  for the previously installed  PTO in the translator module.



















Photo below shows: The 618T-3B Rf Translator module differing from the dash 3 translators by omitting the PTO ( permability  tuned oscillator ) that normally occupied the the visable blank space LHS offcentre.WD40 was applied sparingly to gears to free up autopositioner lower LHS. 


















Photo below shows: The common to all collins 618T transceivers PA module. Here some covers were removed to look for cause of no RF output on 6 and 7 Mhz bands. There were no switch alignment or burnt contact  issues and good condition points to failed RF component.





























Photo below shows: The 618T-3B intermodule interwiring and connector assemblys that are fully accesible by the removal of the cover plate held by two small screws.The damaged 25 pin d series connector can be seen top RHS corner under repair















SSB vehicle installation noise issues were considered during the installation of a standard radio into a deisel 4 wheel drive. Standard practice was followed  and a 2.6 metre surplus military whip and leopard tank base was mounted on the front bumper bar with its associated coupling unit.  Radio mounted inside passeenger cabin with extended control panel . The bonnent was bonded to ground both sides with  braid strap salvaged from RG-214 coax cable. Engine noise was a S4 at times and injector peak transient pulse noise approached S7 . Signals could be worked within this noise regime. However the fitted combination dual battery charger and solar panel regulator produced a S9+20 broadband noise level on 40 and 80 metres. Work was done to bring the 1490-LV unit noise with its 2 modes of SMPS (switchmode power supply) and MPPT ( mean power point )regulation below that of vehicle noise. This unit was mounted in rear of vehicle with near 3 metres of separation.The solar application meant with engine off SSB communications were not possible. 

The following work was caried out to quieten the unit. It was recognised with measurements useing toroidal RF probe on the negative return wire found it  was carrying as much RF noise as the input and load wires. The aim was to bring the chassis and ground return to common point creating a ground reference in the common mode and bypass to that with shortest lead lengths of bypass capacitors . The wiring loom left the unit as a bundle thru a grommet and became wiring tails. This limited suppression opportunities as no terminal blocks were available for suppression capacitor anchorpoints . 

Photo below shows: The environmentally encapsulated main printed circuit board with its pendant cables destined for the enclosure exit grommet. The pre-suppression work involved cutting the negative lead short , fitting with spade terminal, drilling the case for a ground stud bolt near the exit bulkhead. See following photo. The suppression concept was to bypass the main noise wires ( the high current ones) to case at exit bulkhead. 

All the work was to confine RF noise to within the unit enclosure.  All work mentioned would make this unit considered only as a succesfull test breadboard . More elegant implentations could be made if the electrical solutions in this work were still embodied. The suppression measures were fully successfull and the units residual noise fell well below the engine noise. SSB contacts while mobile were satisfactory.























Photo below shows: The fitting of two copper soldering strips, one to the newly added chassis through ground bolt with black negative lead directly attached and the connection point of the red load wire. On these are soldered 9 by 1000pf 50 volt mica block capacitors. The lead inductances are reduced by capacitor parallelling over a single capacitor . 

























Photo below shows: The finished suppressed unit on a mounting plate with added terminal block to allow ease of termination and mounting support for the capacitor suppression array of 11 paralleled 3900pf 500 volt silver mica capacitors with short lead lengths. Note the fabricated copper solder buss attached to unit end plate. A identical copper buss solder strip was anchored to the terminal block.The positive supply lead is cut very short and is immeidiately bypassed . For the low current wires  1 amp pi coaxial noise filters were used , here only one needed. The added ground bolt can be seen on the RHS bottom of the enclosure. All touching paint surfaces of the enclosure metalwork were sanded off to bare metal by a orbital sander. The tough durable paint used was seen to be a insulator. The changeover power relay to solar panels operated by the igntion control wire is not shown but mounted on same mounting plate 

























25th October 2017: HP 85046B S-Parameters Test Set conversion of its 75 ohm bridge couplers to 50 ohms was commenced. Normally these replaced 75 ohm bridge couplers are discarded. The major maintenence and repair of the shack Collins AN/TRC-75 was completed over a three week periodon on all of its constituent black boxes.  The homebrew mains static frequency changer ( see August entry) was installed and tested as a pass for EMI (electromagnetic interference ) compliance.( radiated and conducted) <3uV

Repairs of E-scrap test equipment found difficult previously was continued. A intermittant HP 8757A SNA (scaler network analyser) was completed by process of elimination.  A Collins HF-8014 Exciter was retreived from archive after 10 years storage and  successfully restored to working condition.

Photo below shows : The modifed 75ohm to 50 ohm HP 85046B coupler under final test. Both bridge couplers  were identically modified. Final performance specification was.  Directivity ( in conjuction with  HP8753A VNA connected to the converted HP 85046B to 50 ohm system)  better then  35db 10 Mhz to 1.5GHz (exceeds this test window). Port matching : VSWR : smaller then 1.27:1. See following photos and descriptions . The repaired HP 8753A VNA and HP 8503A S par set is used to develop its own replacement . 




























Photo below shows: A pair of bridge couplers, on LHS the 75 ohm unit from a HP85046B S-Parameter test set under conversion to 50 ohms and on RHS the 50 ohm unit from a HP8503A for comparison and cross measurement. 

The work to convert the HP 85046B S-Par Test Set fully was motivated by work done by K6JCA and others to offsett the high cost of the the HP 85046A S-Par units. The target specification for the finished work is , Frequency bandwidth  3MHz to 2Ghz, (0.3 to 3 MHz reduced spec), Directivity: after HP 8753A calibration >35db, Port matching vswr:  < 1.35:1. This work is in progress.
























Photo below shows: The first stage in the coupler box conversion was to replace the 75 ohm centre female contact assembly in the bridge coupler type n connector , this straight forward process was to salvage the female contact from a standard HP panel mount ( this one has a SMA female on other end ) 50 ohm type n female and replace the 75 ohm one. See the desired 50 ohm contact assembly in the centre of the photo below.  Only the 50 ohm female contact was salvaged and inserted in the existing 75 ohm assembly. 
























Photo below  shows: The very small size of the terminating deposited on glass 75 ohm resistor ( LHS) is converted to 50 ohm by soldering a 150 ohm 0603 SMD chip resistor in parallel. Note the 50 ohm microstrip width. The 1.5 mm width 75 ohm stripline in the CUC ( coupler under conversion) is supplemented in width by pieces of soder wick desoldering braid ( 1.5mm)  soldered to the 75ohm  strips to produce 3mm 50ohm stripline.  The stripline grounding clamp (LHS) was removed during the solder on process of the 0603 resistor to help soldering .  























Photo below shows: The completed 50 ohm conversion of the Port 1 HP bridge coupler from the HP 85046B S parameters test set . No modification of the reference and RF source power splitter is required ( bottom RHS of module). Some parts are barely visable to the naked eye and a number solder tips were used according to heat output or part size involved. The work involved continous testing on a HP 8753A VNA as changes were made . The bridge area  ( top centre) is where most work effort is expended and it is rebuilt as in inset 1.( here the 75 ohms pair of film deposited resistors ( FDR) are bypassed  by a created mechanical structure of SMD parts .One FDR of 87R is scraped off and gold area was removed to create open circuit at the SMA connector.The FDR 44.3 ohm in same areas was just blobbed over with solder.

The stripline was widened by soldering on desolder fine braid to obtain 3mm width .  Blue hatch on sketch. One 75R terminating FDR was bridged by 150R SMD ( surface mount device) to obtain the 50R . Note error in sketch towards top RHS says 87R it is a 75R.























Photo below shows: A Collins Rockwell HF-8014 Exciter under troubleshooting for shorted tantalum capacitors. The exciter was servicable when stored. 

The service methodology was to remove upper and lower covers.  Then measure voltages on power supply terminal strip,  observe short on +15 supply rail. ( volts were +1.3 volts). Pull up all main chassis cards as in photo and note 15volt short clears. Work on synthesiser first,  power was turned on briefly each time a measurement was made. 

Synthesiser cover was removed and  test points point voltage measured , visable in photo exciter LHS front, then front PCB of synthesiser cage with variety of test points. DVM was used on the grey, white, black, brown, red, black jacks, refer to manual .The 20 V regulated rail was at 1.3volts. All synthesiser cards were pulled up except regulator card and fault remained, The shorted tantalum was located under the synthesiser card cage and replaced, synthesiser cards re-inserted . The 20 volt short was observed cleared.   

Attention turned to 15V problem. To locate faulty PCB assembly or module all chassis modules were replaced in this order . The four cards together on LHS of RF translator, then tested for short. Then both audio cards together ( front) and tested, The IF cards right hand side of RF translator inserted one by one, tested, then finally the RF translator in this case was source of shorted 15V. The shorted 47uF 25volt tantalum  near the edge connector and was replaced.

The exciter was tested for RF output and function and ovened oscillator calibrated. The troubleshooting and issues related to tantalum problems in HF-80 equipments are mentioned in this shack biography in different places previously.



























Photo below shows: The HP8757A under repair for intermittant X and Y loss of deflection. The display would develop over 10 minute period Initially nothing then first just a unstable horizontal line then the Y deflection would grow with considerable shimmering and instability then become a good display. Troubleshooting was performed when traces were unstable.   























Photo below shows: The X-Y stroke generator A1 card of the HP 1349A Digital display module. This card contains the X and Y tube output amplifiers and was considered to be the faulty area. The two o/p amplifiers are seen as two clusters of four near the rear of the card. LHS is X and RHS is Y. A number of white topped trimpots are nearby and note the Berg 2 pin brown right angled headers in the centre area of the PCB. These are major testpoints in the signal flow, and checking here showed no loss of  video signals as seen on CRO when no traces were displayed on CRT. Troubles in these areas was experienced before . See diary entry 30th October 2016 























Photo below shows : The A1 card area of X and Y output stages and preamplifier IC's U27 and U28. Both supected faulty trimpots R87 (X) gain and R110 (Y) were changed out based on previous experience and immeidiately the unreliable and unstable deflections dissapeared. These small white trimpots in this particular U27and U28 differential preamplifier outputs seem to be unreliable in 1987 instruments. No problems eleswhere with these trimpots.  On measurement they showed 10K to 50K ohms over their rated values. Note the replacements have been made with higher power rated trimpots visable as larger metal case size in photo. 

If deflection problems and complete loss of either X or Y deflections or noisy ones are noticed and video signals OK at A1 J5 and J4 Bergs headers the suspect the pots R87 or R118. Three HP 8757A SNA' s have been seen with this problem. 

























Photo below shows: A convenient way to work on the A1 card with both side accessible for removing and inserting components. A static strap was worn. Only a few connections had to be removed.  






































13th September 2017:  This month work has continued on both the upgrade of shack test equipment and this test equipment was then used to repair a SDR ( software defined radio ) GEC Marconi H-2550 HF receiver previously not possible. Haveing  no operating,  performance specs or service information, use was made of radios BITE ( built in test equipment ) and general faultfinding methods to locate faulty module and successfully repair the Synthesiser .

 A E-Scrap digital Tektronics TDS 524A 1Gigasample Oscilloscope was also repaired 

GECMarconi  Digital  HF Receiver H-2550 : This receiver was drawn from shack equipment archive for repair for low RX sensitivity, after 10 minutes the fault light illuminated and audio ceased. The receivers own BITE test indicated failure of the synthesiser module. Work was commenced.

Photo below shows:  The GEC-Marconi Digital HF Receiver during initial testing prior hard failure.  























Photo below shows:  The dismantled 2 sided synthesiser module after identification as faulty by BITE test. The sudden failure pointed to a shorted tantalum. Troubleshooting with a DVM  indicated a power supply short by useing ohms range on all 3  power supply rails. The lower card is the one of interest found by elimination. 
























Photo below shows: The PCB card underside during trouble shooting and tracing the source location of the short circuit .The top components were eliminated by strategic lifting  of RFC ( radio frequency chokes) to eliminate good sections of block circuits. The shorted 1uF tantalum was found under the PCB LHS below connector near centre mounting hole. Considerable Rf sheilding was used to compartmentalise the different circuit blocks, even underneath the PCB.  

























Photo below shows:  C87 as the failed Kemet 1uF 35 volt tantalum electrolytic capacitor.  For this late model doinantly digital surplus radio ( 1994) it was necessary to be aware of static damage concerns and the use of HRHS ( high reliablity hand soldering ) methods due to the complexity, multilayer and miniturisation of the components.The faulty capacitor was replaced and bus short was seen to clear. All disturbed areas on PCB top surface were restored .

























Photo below shows : The PCB refitted to the module housing with all overhead sheild enclosures. 














Photo below shows:  The re-assembled GEC Marconi H-2550 receiver post synthesiser repair undergoing check of reference oscillator operation and accuracy.









































Photo below shows : The rear view of the the GEC-Marconi HF receiver and its seven constituent modules plugged into mainframe. The interface between module and mainframe is the use of DIN series connectors 

























Tektronics TDS 524A Digital oscilloscope repair :  A Tektronics TDS 524A digital storage colour CRO was recently aqquired as E-scrap and after cleaning repaired for failed power supply and very dim display.The CRO mains operating voltage is very wide 96 to 250volt ac without adustment When switched on the traces were dim and display barely viewable in daylight. The Tektronics TDS-524A (module level) Service manual was downloaded for the CRO. The outside cover was removed and the preset brightness control ( small preset near fan) was adjusted according to manual and gave a useable display which was a quite striking result.  Shortly later  the CRO refused to turn on and ceased working.

Photo below shows: The A17 low voltage power supply after CRO dismantled during repair process, circuit schematics were obtained by downloading the TDS 520 CRO schematics, component level repair manual package from the net. The circuit is close to identical although component placement is different . The component designations were found to be the same. The major positive feature of this supply was it is self contained and can be operated stand alone. Pins J5 3 and 5 are momentarily connected to start and stop supply. See schematic.  

The A17 power  supply was connected to a isolation transformer via its IEC connector  and powered up. rectified HV was present and main mos switches not shorted. Interest centred on the Standby supply and suspected not working, visual  inspection of the PCB area near Q9 showed considerable heating of solder pads of the two series TVS ( transient voltage suppressors). The associated  device, Q9 a BU508A HV bipolar transistor was found shorted ( photo below see the area LHS  forward edge of the chassis box with the large electro in it ,that is Q9).

Both TVS and Q9 were replaced, power supply switched on and standby voltages OK. Fault was TVS leads melted solder over number of ageing cycles  and created high resistance joints, failed to protect Q9. This standby supply operates 24/7 since this CRO came from manufacturing industry rack mounted application. 






















Photo above shows: The A17 Tektronix power supply module, Dead centre of the module is the T3 standby power transformer associated with Q9 BU508A , close to it are the small components for the three powers supply voltages needed for the keep alive circuits prior to turn on.( including the  mains boost converter) The IEC power connector and filters are RHS lower left. The right hand 50 % of the board are is the input and power management . The left hand 50% are the multiple isolated voltage supplies .The rear power switch when on powers up the RHS 50 % of the module. On either 115 volt or 230 volt the HV is around 410V dc. 


Photo below shows : Top view of the TEK TDS 524A CRO during refitting of repaired power supply. This entire open area becomes covered by central plate on which is mounted the A11 DRAM master PCB.
























Photo below shows: The A11 Dram Processor Display PCB  installed less rear backplate assembly, take note of RHS, this area has the major connectors J26 and J27from Aqquisition PCB and  A17 main power supply module below.  Nominated by manual where the CRO LV supply voltages were measured, ( all top connector rows are odd numbers) at the very rear a PCB projction can be seen standing up. ( correct orientation ) Make sure this linking PCB is not assembled upside down. As happened to VK2BLC.   
























30th August 2017: Collins AN/TRC-75 Transceiver major maintenence: This month after a failure of the CU-749 ( 180R-6) antenna coupler. A complete performance and ramp testing of the overall TRC-75 system useing the support test sets ( ramp TS-1325 for C-2848, TS-1325 for R-761 and T-730, Bench test set AN/URM-124 All system modules, was undertaken.  A new energy saving 3phase 1500VA 400hz mains direct frquency changer was fabricated to replace the static aircraft 400hz inverter lead acid battery combination and is undergoing testing .

The Collins AN/TRC-75 HF 28,000 channel transceiver is a fully automated radio set  including  power amplifier and antenna coupler and does not have any operator tuneing controls. Operations is simply select frequency , press PTT and wait for tone to stop  and select receiver volume. 

Units were then serviced for CU-749 coupler (  broken  192 degrees lost motion operating spring), coupler had failed without warning.

Given this failure an extensive test of performance and operation was performed . 

T-730 amplifier( poor hum and noise specification), found noisy 4CX250R  tube, low output power (800watts) , poor tube balance, (> 70mA) replaced all three output tubes and acheived balance within 7 mA static and OK and tracking at 600mA. Replaced  faulty PA tank servo motor and rate gen. 

Coupler controller  C-2848 ( 2 sec delay relay failed) causing CU-749 to malfunction. Fitted new thermal relay. 

R-761 general tests all modules in the URM-124, re-aligned 1528 RF rack in the GRM-10 test bench,  adjusted RX servo modules gain and balance. Calibrated RX frequency standard , tested all tubes in 1528.


Photo below shows:  The T-730 RF power amplifier on the hardware bench during PA servo motor replacement













Photo below shows:  The mechanically disassembled servo motor PA assembly ready for electrical disconection centre of photo 























Photo below shows:  The Collins T-730 power amplifier PA stage in detail , the relay and strapped carbon rod resistor RHS lower are used during tune cycle to cap the PA VSWR  to a useable value until the antenna coupler can deliver a workable impedance. Without that resistor the system could never automatically complete a tune. 
























Photo below shows:  The T-730 amplifier  6CL6 driver tubes output servo tuneing assembly ( centre)with colocated position sending servo potentiometer. On the RHS leading edge are the vertical triple stack of PA tube screen balancing resistors switched independently. RHS lower is the PA stage band switch motor. 























Photo below shows: The T-730 three paralleled 4CX250R PA tubes . The 47 ohm resistors with the paralleled coils are the parasitic oscillation supressors .

























Photo below shows: Some service aids used in the repair and maintenence of the R-761 receiver RF rack and deck assembly. In the centre middlerear  is the Starret dial gauge used set the upper and lower end stops for coil slugs moving platform . In the front is the tube extenders kit and chinese finger trap tube pullers. RHS is the tube tester used every time the 1528 rack fails sensitivity spec, it used  on selected tubes based on test point voltages. At least every 3 years a full test of all tubes is carried out  followed by a full rack alignment .Tubes are replaced when transconductance is below 50% .They also receive life predicting test where the filament voltage is reduced  1 volt and fall in transconductance  is noted . 


















Photo below shows:  A emphasis is on measurement  and mechanical alignments required by the precision servo systems in the Collins AN-TRC-75 radio set. There are six  servo positioned  systems, In the ( R-761 receiver exciter), one each for the synthesiser ( 4000 precise stopping points) , one for the 1528 RF tune-rack. In the (T-730 RF Amplifier)  one for the driver tuneing and one for the PA anode tuneing. (PA plate signal to PA tube grid is servo maintained at 180 degrees). In the ( antenna coupler  CU-749) one for tap positioning (final match magnitude ) one for the ceramic bulk inductor (susceptance) . Following mechanical alignment the electronic parameters are calibrated into the system by adjustment of 10 turn follow up potentiometers. Use is made of a sensitive differential input AC millivoltmeter . A  AM-1528URC module repair workshop occurrs when the numbers of failed rf modules accumulates.
























Photo below shows :  The Collins R-761 ( AN/ARC-58) HF receiver rack .(AM-1528 URC)  Derived from the R-390 receiver,  this bi-directional module is fully and automatically servotuned. Essentially the performance heart of the receiver.































Photo below shows:  The AN/TRC-75 Receiver exciter R-761/ARC-58 during final level repairs to gain a LRU . Always one LRU  ( line replaceable unit) is required to support VK2BLC TRC-75 in service. A failure of the ham station radio has a MTTR ( mean time to repair of 15 minutes and this initiates the processing of a serviceable LRU to repeat the cycle. The WIP ( work in progress) tag visable LHS unit tracks with the unit as the work is modular as well. 



















Photo below shows : The direct mains 1.5KVA 3 phase 400hz frequency changer under development useing manufactured modules and homebrew input  to create a improved energy saving strategy to operate the AN/TRC-75 radio set. The single phase input is translated to radio  compatible power at around 86% efficiency . Previous system of aircraft inverter and battery system and mains charger are replaced. Previous to that used a Bucknell 5KVA motor generator set  and initially a Jatz and Heintz  2500VA rotary inverter from a Hercules aircraft.  

Currently the the  changer output is transformerless and some phases have different loads , a 3 phase Y output transformer will be tested to get some phase to phase load  intereaction and improve stabilization of  the line voltages. 























Photo below shows: The homebrew shack replacement energy saving mains driven Collins AN/TRC-75 AC frequency changer under development to solve the impact of unequal phase currents reduceing output power and failing to drive the TRC 75 to licensed operating RF powers. Solid state converters were found to have no electrical equivelent of the mechanical property of inertia and overcurrent sees output completly trip. The test set-up photo centre shows the 3 phase analyser, prototype isolation transformer, probe and true RMS Fluke 87 DVM. The load is distant on the shack 400Hz power distribution network.   

The mains compatible freq changer ( front centre photo) will operate the Collins AN/TRC-75 directly from the 5KVA homebrew solar system replacing the current configuration of 50 Hz mains to DC to 28V battery then DC to AC 400Hz  ( 3 phase inverter) ( rear centre photo) improving efficiency and lowering losses. The DC systems in the background centre are no longer required. The inverter batterys will become standby TRC 75 power supply.



















Photo below shows: The BWD 881 powerscope displaying the 3 phase 400Hz freq changer output full load waveform with the TRC 75 on transmitt into 50 ohm load in vestigal ssb AM mode with a radio supply power of 1500VA. Note the sine phase shapes in the previous photo are now ones of trending to stepped wave.  The analyser allows observations of all phases simultaneously for different load conditions. 























Photo below shows:  The 400 Hz common cored isolation transformer that successfully solved the inability to  drive the Collins TRC 75 with a 1500 VA rated solid state converter by allowing surplus power on lighter loaded phases to divert their power to the heaviest loaded phase and boost its line voltage. The 1st order action of the WYE connected  3 limb transformer was to equalises line voltages. Successfull since the C phase was 108 volts on the changer side becomes 115V on the equipment side with 1500 VA load. The 2nd order action was seen to reduce harmonic distortion over operating range.   The DVM is not in use in photo. The Collins AN/TRC-75 now works all modes for legal powers.  

























Photo below shows: The homebrew frequency changer on successful final test before casing. the unit wiring completed,addition of  4 indicator lamps, incorporation of 4 wire PI noise filter, and 1500VA isolation transformer. Unit on top RHS is 28 volt DC 20 ampere supply. The low cost Brother labeller LHS is used for all labels on the three different white on black label widths 12 mm, 9mm and 6 mm . The 6 mm makes very professional radio front panel lettering of correct scale .

The availability of solid state 3 phase mains operated power supply solutions has made powering of surplus aircraft transceivers more usefull and possible. Collins radios  618T-1 (3 phase 208V 1KVA)( 400 watt PEP tx) , Collins 628T-1 and 628T-2A ( 3 phase 208V 1KVA) (400watt PEP)  and Collins AN/TRC-75 (3 phase 208V 2.5KVA) (1000 watt PEP ).  These radios are offered at low db because of powering requirement.

The addition of noise filters input and output and use of EMC considered construction (attention paid to ventilation openings) of cabinent (hardware Electro Magnetic Compatibility) can produce a CISPR ( international comittee radio interference standards) compliant power supply package (suppessing the switching noise from converters). Certain types of of AC motor drives ( USA) ( will work fine if sine output). For australia the issue is voltage incompatibility since ozz 3 phase is at 415 volt. Some customisation and circuit redesign or addition is required 
























31st July 2017: Harris HF transmitter system RF-130-02 removal from archive and commissioning. System elements comprising RF-110A, RF-124and RF-1310 were removed from long storage and assembled.  After plugging up all the system components extensive reference was made to the Harris systems manual RF-130-01/-02 1KW HF transmitter instruction manual ( Harris publication 101121-0022, July 1985, )

The basic process was to set all equipments mains voltage settings (for Australia). The RF-1310 two mains setting locations external plus internal A23 24 volt power supply. RF -124 power supply  primary taps internal to RF-124 (note settings available for 242V).  Note there is a Harris field advice bulletin to correct wrong jumper information in the 101121-0022 manual.( Listed as a manual ADDENDUM L546, July 1986). RF-110A power supply strapping was completed. In the RF-1310 all DIP switch set-ups were made for the desired operating options. RF-110A rear J8 connnector was jumpered enable keyline interlock. This one was important.

When power applied standard australian 10A plug was inaquadate for the 20A powering requirement during commissioning. When system is fully serviceable and RF power reduced a 10A  plug will be found satisfactory. On power up, the HT failed to appear after the 3 minute timer for 1500B tube filament warm up.  It was necessary to analyse the problem. The problem was found to be alignment of the RF-124 cabinet interlock Despite a simple fault some service effort was required to diagnose it. 

Interlock faults are difficult to trouble shoot since wiring continuity checking involves probing sometime difficult to access wires and contacts. The RF-110A contains a terminal block area where system interlock wiring faults were easily acessed and diagnosed. See following text and photos


Photo below shows: The ham friendliness of the RF-130-02 system with its ease of service access and no special tool requirements, just a manual and a multimeter and 50 ohm dummy load. (The RF-1310 has a signal generator mode available for gaining a cw source independent of RF-1030-02 control circuits for driving the RF-110A or testing the RF-1310 itself)  
















Photo below shows: The RF-110A tilted for service access to terminal strips under insulated cover rear chassis second from bottom.

RF-110A Overload lamp problem:  During soak testing and cycling the RF-110A  overload lamp illuminated and locked the amplifier out and couldnt be reset.The problem was non operation of the input air duct vane switch as it  failed to operate in the airstream. This stickyness of the air vane microswitch was related to non use or long storage. In the photo, the vane switch access metal bung can be seen near the  RHS lower edge of the "CAUTION" label (top LHS chassis). This was removed to observe vane operation when blower operating. CRC-5.56 lubricant spray can with small tube attached was used to spray the microswitch moving shaft to free the air vane . 





















Photo below shows: The service sheets from the manual laid out for troubleshooting the loss of HT
























Photo below shows: The terminal board area 1A1TB1 and 1A1TB2 strips where measurements were made to diagnose missing control interlock






















Photo below shows: The operating voltage transformer strapping area (RHS lower) . The centre  lower area is where the RF power management is calibrated. Both APC (automatic power control) and PPC ( peak power control) are set.  
























24th June 2017: Hewlett packard HP8662A  Among tasks this month repair was made to the shack RF signal generator 70 db attenuator  and the remote receiver site VHF link duplexer filter was aligned to frequencies in use and performance specification verified .

The HP8662A  RF output was very lossy when set to 0dbm produced <-80dbm and when set to +1dbm rf output was correct at +1dbm Work was done useing the 8662A as a test source of RF and control signals to locate and correct faulty attenuator .

Photo below showsThe 8662A front panel if lowered both attenuators can be removed and set up on top of the instrument. In this case the HP8662A was used to conduct a attenuator repair workshop. 

 The RF output was observed on a spectrum analyser and while observing the trace, and feeling the operating vibration of the attenuator indicated the 70 db attenuator on the LHS marked #3 was identified as the faulty unit. The attenuators are packaged as sets assigned to one HP part number.

























Photo below shows :  The 8662A being used a test RF source and controller and test bed for the trouble shooting of the 70 db attenuator marked #3 above. The dismantling procedure for the attenuator was viewed on U-tube and found very helpful.  

The RF stripline panel with deposited glass attenuator pads  is a separate assembly lying just behind the main atten chassis . The atten chassis is inverted and the complete strips of gold tipped moveing contacts can be seen easily and watched for their movements and height when actuated. In this case the 10 db section ( closest to the rainbow cable end ) was open circuit when selected. One contact failed to touch the substrate. The fix was to precision bend the contact and add a flex bias to raise its height to same as its operating mate. ( 2 contacts move in pairs to touch the glass subtrate of mateing resistance pad) . The assemblys was assembled , tested and refitted to the 8662A.
























Photo below shows: Close up view of a section of the HP attenuator contact system after repair. The attenuator separates into two distinct assemblys , in the background the small dark patches are the glass like small attenuator subtrates with deposited resistances. In forground a contact pair can be seen clearly , these mechanically agile strips either have linear short or contact with the attenuator pads. The contacts are shown in pad connect position post bending  and can be seen to be set at the same height. The attenuator under repair coils are energised to verify that when contacts are switched . The contacts fall with positive mechanical pressure and short on the lower bypass bar. 






















Photo below shows: The remote receiver site 2 metre link homebrew duplexer undergoing final test. The test instrument is a HP8753A VNA and top trace is the impedance plot S[1.1] looking into the reciever port, The trace is the ideal cardiod shape with the dimple indentation sitting on the 50 ohm non reactive point of the smith chart.( at RX frequency) . The lower trace shows the  pass response [S2.1] to the duplexer antenna connection. The receiver path uses series resonate tuned circuit resonate at the TX frequency . The signal passes through 2 sequential cavities, each in notch mode ( useing johhanssen ceramic trimmers) (see earlier descriptions much lower down in this blog) . The trace falls sharply after the pass frequency and the deep notch appears tuned at the TX frequency . 






















The Photo below shows : A close up view of the transmit path trace after the final adjustments. The insertion loss is 3.4 db , VSWR is 1.2:1, the rejection of  the receive frequency in the transmit path is -86db plus the rejection loss in the notched two sequential TX cavities in the receiver path which yields over -100db for the 600KHz frequency spacing between the TX and RX frequencies. 

























7th May 2017: Hewlett Packard HP8753A Work is continueing to complete upgrade of shack instrumentation. Vector Network Analyser also part of the E-scrap bulk was recovered to working condition following similiar processes mentioned for other instruments. The missing front and side handles, feet, and rear bumpers were replaced and unit serviced for following faults, no display ( repaired 1349A monitor module A18) , wouldnt phase lock on reference signal ( repair phase lock module A11), repair front panel ( A1/A2) . Full schematics package utilised from net. 

The  main application for a VNA in shack is the characterisation of ferrite loaded inductors and ferrite loaded semi rigid based RF transformers used in the design of high power LDMOS, CMOS and Bipolar based linear amplifiers. These components and their operating Q, bandwidth and loss factors are critical to amplifier stability. Many unidentified ferrite materials such as toroids, bars and E sections have been salvaged and need identification to match to end use. Additional test jigs are added to the 8753A to allow dc current to be applied simultaneously to the ferrite if required. 

Another application allows optimisation of homebrewed power amps designs and see the 8753A built out and buffered ( additional high power attenuators, instrumentation power amplifiers )to plot driving power VS frequency VS DC current input VS RF power output sweeps to obtain frequency linearity and establish feedback network values and circuit behaviour. 

Finally the design and verification of HF amplifier low pass filters to get the crossover knees in the right place, ultimate attenuations and observe undesired stray coupling across the filter sections. 

Photo below shows: The completed HP8753A VNA with non assigned HP8503A S parameters test set offering full performance to 1300 MHz for the combination. 






















The main delay going forward was aqquiring a HP85046 Sparameters test set with a disproportionate db cost. It was noticed the more available HP 8503A S parameters test set met all the parameters to 1300 Mhz except had a non compatible port configuration . It was decided to use the 8503A and custom homebrew the 4 phase matched link cables.

Photo below shows : Homebrew rigid mini coax type n female to N female link cables fitted . The construction used type n connectors from Murphy , salvaged and refitted to precise cut 4 lengths rigid cable ( 204.3 cm each) , kept straight and bent last. The stripping prep is repeated for 8 ends identical and when connectors were assembled the centre pin alignment ( depth viewed from front) was noted and reproduced. The RF cable has different bend locations compared to other identical three. A brother labeller with 6 mm white on black tapes was used to name cables.






















25th April 2017: Hewlett Packard HP8643A RF Signal generator was the second last unit recovered from E-scrap. Following the work on cosmetics  Note was taken of the service methodoligy for this signal generator that uses its built-in powerful diagnostics to do the fault finding. The self calibration capability automatically monitors and compensates for component and performance drift untill the generator system can no longer maintain operation. This results in fault codes that signal the faulty module or required action. These codes can be looked up. The on-site service operation consists of removing top cover and setting DIP switches to service mode and taking futher actions. The system may then advise user to send unit to service centre  if not resolved.  

Post 1993 HP instruments moved to these more simplified ( sophisticated) modular service approaches and discontinued releasing component level technical information and schematics.  The mixture of analogue thru hole and surface mount and full digital control makes understanding and estimating just where the fault is very difficult if no visual signs of fault are apparent without access to this information.

The fault code indicated "+5,040.1nn " was cross referenced to the look up table list as REF OSC STD ALC module. The indicated module was aqquired as a part, replacement made and allow the automatic processes within the 8643A to bring the unit to serviceability. Opening the module did not visually reveal the fault. 

This was 180 degree deviation from standard processes of understanding operation and focusing on most likely one low cost component to restore modules to operation. The repair was found to be straight forward. However finding and obtaining low cost replacement modules is much more difficult.  

A special thanks to Bill KA3AIS for helping in this regard. Purchasing of two E-scrap units prior to starting work is highly recommended for HP8643, HP8644A and B series used and not working instruments which have a insertion loss of around 3db per lb weight. (125-165db) each and share many common sub-assemblys. Refer to module level HP manual . 

The special properties of this sig gen as well as its superior phase noise lies within option 007 which has a tsunami of modulation capabilities.

Photo below shows : The recovered HP8643A rf signal generator under test after repair. A second panel assembly was the source of the replacement elastemar keypads, these were carefully removed and refitted to the generator under test to the right.The rejected parts were refitted to the source panel assembly and reassembled . This repairable sub assembly was then archived to preserve displays and PCBs . 























Photo below shows : The front panel assembly sandwich dismantled for repair , The switch contacts are printed on the top most PCB and lie on top of the elastemar key panel . The display and decode PCB assembles on top of that. The different screw set for both tasks are marked on the card. Care is needed in maintaining cleanliness in this operation.























Photo below shows: The elastamer membrane system with moulded and printed operating keys. The separated rubber keys when broken free are not individually repairable and complete pad needs  to be replaced.




















Photo below shows : The interior of the signal generator which features a large delay line on the LHS, service method is to replace the complete module. The cabinent is basically the same for all models  differeing in the population of modules. The 8644A uses a different attenuator module ( 2nd from unit RHS).  The 8644B model uses two delay lines. The lowest phase noise variant with extended frequency range sees every slot filled.























17th March 2017: Hewlett Packard HP8662A  RF Signal Generator recovery from E-scrap. Work was continued to repair and restore instruments aqquired from E-scrap to replace and upgrade shack test instrumentation. The back ordered parts for the  HP 8662A had arrived ( 3months) restoration was commenced. The unit had poor cosmetics , missing  cabinet hardware(feet, handles,rear plastic bumpers) was very dirty,had many stickers,packing tape residues,  missing on/off switch, knobs and scratched and paint free patches on front panel. First task was to repair the power supply.

On test vaporised power supply fuses, had failed power supply. Post repair of power supply had malfunctioning CPU, post repair CPU had 50 db of output signal loss. Following text traces work to  restore unit to seviceability.

The HP8662A signal generator was seen to be  built to a high mechanical and electrical standard with long life components, embodied service and maintenence friendliness. Full component level documentation was readily available and a degree of hardware standardisation allowed module extenders and parts to be sourced from the support kits of a whole family of possible similar era HP instruments. These  factors made  this signal quite ham friendly. Was a suitable choice with performance to replace  a HP8640A with their ageing plastics issues.

Most of VK2BLC service effort was in devising the repair  methodology of the HV  A7A3 PCB card and HV A7A4 supply motherboard of the power supply assembly. (Limiting the damage done when repair was only partially successful). The RF systems, the most complex part of the generator was found to be free of problems and some issues with back up battery RAM and ROM were found. For example failure to boot and display sequence freezing.

The recommended service approach is to purchase a  parts unit to support  the operational one. These units  have low purchase value when not working. Around 7 db per KG ( 2.2lbs) .

A mention to be made of the Cons of the  later instrumements the  HP8643A ,HP8644A and B and extended frequency versions of high performance generators have no component  level  service information or detailed technical descriptions available and had very large cases . The Pros of BITE ( built in test equipement and diagnostics ) was  a powerfull help to locate faulty modules , however finding module assemblys was a another matter. The compact size of the HP8662 and its ease to service was considered  a definate plus.


Photo below shows:  The A7A3 HV card of the HP8662A on service bench for repair. On the near RHS the HP8644B  previously restored from E-scrap can be seen. Below that is the first restored HP8662A also a restored E-scrap unit . The HP8662 this text refers to is the restoration of  the  E-scrap parts unit itself based on the knowledge gained from first one. On the RHS is a HP89410A VSA used to analyse the spectral purity of restored generators  It is shown displaying the spectral output of the HP8644B sig gen . The unit is scaled 120 db vertical and 10 khz span  in 3 hz bandwidth . Measured value of phase noise displayed is  -120 dbc/hz at delta at 1KHz. The HP8662A has a spec of -121 dbc/hz at 1Khz
























Photo below shows: The A7A3 HV inverter card and new repair parts. . When trouble shooting this card it was found important to test all the semiconductors and that may involve removal of the transistor or lifting diode leads.(  useing the DVM diode test) . Pay particular attention to the two driver transistors in units with blown output devices.Th red heat sink will need to be dismantled on other  side of card for access.

 The main failure was found to be caused by the 22uf 350V axial electrolytics having low ( 4uf and 0.5uf respectively) and uneven  capacitance values. This caused the output transistors to have unequal high level signal voltage division ( deduce failure mode  by tests showing dead shorts between Collector and Base)  leading to a cascade fault sequence. ( power output devices, base fuses , driver devices. Attention was paid to  resistance checks of all main high voltage electrolytics bleed resistors.( A7A4 and A7A3)   A capacitance meter was used on all low output voltage filter caps which are less critcal .  In the photo below the blue 22uf  capacitors are recommended over the 22uf grey ones. They have superior seals against electrolyte loss. Refer to service manual for detail.

Before module was removed for repair, testing of the HP8662A was made  , a visual inspection of the A7A3 card was made and after market power transistors devices tested for shorts with DVM and appeared OK. Unit was set for 240 v and fuses were vaporised on switch on. All futher serviceing and testing was done with unit set for 115V useing step down transformer to limit fault currents . When all instrument service completed was set to 240 volt.





















Photo below shows: The HP8662A under trouble shooting  with  CPU extended under testing for failed boot up sequence. Shown on the  LHS is the HP11714A  HP8662 Service Accesory Kit. Notice on the RHS front pocket of HP11714A Kit  the extender for the A7A3 HV card which has a HV DC isolating safety switch mounted on it . This enables  HV dc to be removed from A7A3 card while testing  output devices driver waveforms.  On the RHS the front panel of the 8662 folds down and the RAM battery holder for earlier models can be seen centre left of the 8662 sig gen.

























Photo below shows:  A2A6 CPU card extended from the 8662A .The fault was frozen and intermittant nonsense display during initial boot up on switch on . This  early model gen had incorporated Change 42 (1985) which saw a later RAM /ROM  card designated  A2A7 retrofitted and earlier cards discarded.   The RAM keep alive 3V battery residing on the A2A7 RAM ROM card was checked first and OK . The ram battery location had been changed from instrument front to on card A2A7 mounted.  

Test methodology was to measure DC operating voltages and check clock waveforms of A2A6. ( the CPU is heart of instrument control)  without extending card . A basic familirisation of CPU operation is aided by look at the motorola MC6802  data sheet and referencing uP pin signal definitions with HP manual info. Of interest are the ramp  signals that control the initialisation of the ROM start address and clock waveforms.

The  test points shown on the top LHS of the card are  sequenced left to right. The front panel displays act as indicators to  analyse what is happening. The manual has some quite involved procedures . The simpler initial approach is to take an interest  in the CPU card behaviour. A Oscilloscope was used for measurements on the testpoints. 

TP1 (test point)  SA2 is logic enable to indicate valid address control to ROM originating from pin 5 VMA of uP.   This was missing.  Clock waveforms were all OK . Power up ,power fail and  , clock fail detectors were checked and not inhibiting valid address confirmation from uP VMA pin 5. The uP failed to respond to hard reset and became suspect. 

A very close inspection showed when the socketed uP had been replaced one  pin was bent over and not contacting the socket. Using antistatic strap  and extractor the 6802 chip was reseated and the instrument booted up normally.  It took a number of stop and restart cycles for displays to normalise and odd decimal points and  occasional stuck digit to extinguish.

























Photo below shows : The HP8662A operated correctly but was showing a 50 db loss compared to panel level setting. Service methodology was to check output at output module A4A1 , was +16 dbm so OK ,  Note that despite a large signal loss the output was under attenuator control so suspect reverse  power protector. A2A11 , check ramp control voltages and find OK, As  protectorwas part of attenuator assembly a way to check without dismantling attenuator was found.

 A HP8753C  VNA ( vector network analyser) was used to analyse the  RF ouput at the Type N connector and a RF non reactive  short was indicated. The SMA semi rigid was suspected and disconected and short cleared , the VNA was moved to directly testing output impedance and attenuator S[2,2] was better then 30 db all atten settings. A close look at the type n connector assembly showed a very  fine gold strand  shorting out the SMA socket . See photo .

To fold down front panel remove  front panel surround screws 2  top, 2 bottom, left hand side front handle screws (4) , left hand and right hand large front carry strap screws ( one each side)  and   major retaining  nut on RF output connector then slide whole front panel forward then fold down.

The photo below  shows the RF attenuator RHS lower and the N type RF output connector on its mounting bracket .























Photo below shows : The small pure gold filament shorting out the HP8662A sig gen output type N RF connector responsible for the 50 db  signal loss.




























Photo below shows: The repaired HP8662A and completed cosmetic work with the unit veryclose  to full serviceability. A number of general  tasks was required to complete the 8662 restoration .All missing cabinet handles front and side and feet and screws had been fitted earlier to allow ease of handling.

The very dirty top and bottom covers were scrubbed with good quality soap impregnated  stainless steel wool and then sprayed with Armoural classic protectant to refresh plastic coatings.The front panel stickers/ masking tape  were removed with care with a mixture of mineral turps and methylated sprits as a tame removal solvent to preserve HP panel lettering and markings.

The front panel was wiped with methylated spirits  then masked up to allow spray painting for small paint loss areas using model master  FS 16440  flat gull grey model paint . Then whole panel was  sprayed  with Armourall classic protectant including perspex window and wiped off . The missing on off switch was replaced with a C&K similar mounting type paddle switch.

The Reference oscillator was calibrated and the signal generator was serviceable.


























Photos LHS below shows a non standard HP part. Was a C&K SPDT  toggle with handle switch used to replace the  missing 8662 A power switch. 

The RHS shows Modelmaster spray paint used to repair paint finish on front panel. The paint was  Model Master   FS16440 Flat Gull Grey, 3 ounce  can.






















23rd February 2017: Rockwell Collins HF-8054A HF Communications Receiver recovery from long term storage: A receiver was taken from 10 year storage and was returned to serviceable condition. The work and procedure taken is mentioned here. The experience of previous work on HF 80 receivers was applied , that was attention to  cosmetics , correct function and finally performance was carried out.   Failure of radios circuitry is  inevitable and extensive if full voltage is applied initially. A suggested procedure is mentioned below. There will be still the odd tantalum that will short . The service methodology that was used to locate these is also mentioned .A total of 6 caps were found to be shorted  after the tantalum conditioning procedure.  3 in B2 IF , 1 in the A1, IF 1 in the sub carrier gen and one in the 1KHz divider. Only the the faulty cap needs replacement . More text on HF-80 tantalum cpacitor failures can be found much lower down this diary in 2011 entries. 


Photo below shows: the completed receiver, initially it was in need of freshening up.





















The initial cosmetic work was clean all the bare aluminium surfaces with methylated sprits and wipe clean to not leave any residue, the top and bottom cover was removed to access controls and switches and pots and CRC-2-26 was used generously to free sticking controls and lubricate switches and potentiometers


Photo below shows:the restorative effects of useing the armourall (classic) product in revitalising the pigments in the  front panel paint

























The tantalum conditioning procedure: ( for long stored RX) The following sequence was used .

1. replace the two lamps in the s-meter.--the  relative lamp brightness changes dramatically when board shorts occur. Observe lamps for this at all times.

2. Run the receiver on half voltage for 3 hours minimum. As Australian voltage is 240 volts a 115 volt step down transformer was used. Measure  at power supply TB1under chassis TB7,6 ,1,8,3 and 2. The voltages although low , check non are at zero volts or say 0.2volt indicating a immeidiate short.If so carry out step 4

Initial first powering:

3. Apply full mains voltage and verify voltages at power supply TB1 are normal at Pins 5 (+5V) ,6 (+8v),1(24v), 8(-15v),3(+15v) and 2 (18v)

In the first few minutes of operation watch closely at s-meter brightness , a few  tantalums were observed to fail in first 3 minutes. The display will go dull or a loud hum may appear in the speaker. (audio on A1 , RF gain fully CW,  ISB selected and volume advanced ). If this happens, immeidiatlely turn off receiver.

Locating failed tantalums (the cards they are on)

4. Pull up all IF cards and test briefly again. IF OK replace one by one ( turn receiver on and off each time to re-insert PCB) . Leave any bad PCBs up .

Apply power and use DVM to measure ( forward end of synthesiser frame) synthesiser voltage regulator PCB top test points.( TPs count 1 to 13 left to right).

Check TP12 (+20v), TP9 (+5.2V) ,TP10 (+24V), TP11 (+8v), TP13 ( DVM ground) . Monitor these occasionaly for firsts 3 minutes. If any go low turn off rx and pull all cards up ( see photo below ) . Turn rx on and off while re inserting card one at time to find bad PCB. Photo shows receiver operating and powered with bad circuit cards up .

General hints to most common shorted tantalums

5. Only the tantalum capacitors directly connected to voltage rails will found to be failed. The Collins repair manual schematics and associated overlay sheets were used to identify the most likely capacitors .

6. Failed capacitors will have resistance of around 0.5 ohm. Use a DVM as ohmeter to test them . Use a properly set up antistatic test area ( mat) on which each pcb will be checked.

Test at the PCB  rail voltage inputs series inductors . Check resistance between rail and ground. These inductors  are the reference measurement point to observe rail shorts.

As  each suspect capacitor one leg is lifted and capacitor cleared or otherwise keep lifting and testing until the actual rogue cap is found.  Measure effect of rail short  at the main PCB rail voltage feed point inductor and ground until resistance goes high. 

After the odd  shorted capacitor was  identified and replaced  all other lifted caps were resoldered. Only the faulty tantalum requires replacement. Tant caps are long life devices.  Care was taken  with HF  80 printed circuit boards , useing  correct solder tips and temperature settings to avoid track and eyelet damage.  


Photo below shows : the 19 plug in cards assemblys cards in this build. The most common cards to have shorted Tant caps are IF PCB assemblys and divider PCBs. The cards are numbered from far rear directly forward to synthesiser cage and then from right to left in the cage itself. 





















Photo below shows: the concept of of lifting PCBS or assemblys with shorted tant caps. Once all voltages were  normal attention was turned to locating the exact shorted tant cap in each assembly or card.




























Photo below shows: the B2 IF assembly and PCB . A large number of tant caps can be seen ( blue , red, black  and orange bead capacitors) . The three voltage rail input green axial  inductors can be seen at rear centre near edge connector. Measure between these and ground for low  resistance indicating rail short. Suspect any one of the nearby 9 tant caps as the rogue one.  

























Photo below shows: to actually see a burnt out shorted tantalum capacitor is a rare sight. Normally the affected shorted tant capsjust  look like a normal one.  The capacitor was partial short and was burnt over a long time period.  Notice the construction with a centre drum electrode surround by 360 degrees of dielectric.
























Photo below shows : the test and repair bench set up with  Collins HF-8054A powered up and the procedure mentioned in text above in progress to locate shorted modules or PCBs . The brightness changes in the s-meter illumination level is one indicator of shorts occurring. Shorts have to be identified quickly and power removed to save burning up the voltage rail  supply inductors. Most tant cap shorts will occurr withing 10 minutes of applying mains power after very long storage. Just one or two will be found (. If some attempt is made to condition the powers supplys and filter capacitors at lower mains voltages for some hours before full voltage application -see above text). Note the use of the antistatic mat and wrist strap while performing any work or desolder operations on HF 80 PCBs.























31st January 2017: A quiet month with no construction, mainly taken up by searching for and the aqquisition of required parts, assemblys and modules to continue repairs to HP test instruments aqquired as E-scrap. HP 8644A, HP 8662B, HP 438A, and Tektronics TDS-644A

26th December 2016: Harris 590A, R-2368 URR HF receiver hangtime modification was devised and implemented  to allow operational compatibility with co-located ssb transmitter. Attention to receiver hang time functions were made during this last month. The circuit operation was analysed with reference to the Harris manual and the 4538 single shot multivibrator  IC datasheet used for the hangtime function.  The simplest and most effective control approach was taken and is described below.

It was found all  Navy surplus  sourced R-2368URR receivers had a over long (3 sec) hang time when in the SSB mode useing slow AGC speeds. The effect of this was to put a unacceptable time delay into the transmitt to receiver PTT operation when useing separate colocated transmitter. Useing medium or fast AGC settings did not provide good SSB listeneing and still had some SSB pumping of received signal. The slow AGC function time constants were definately well optimised for SSB  however not realisable due to hang time issues .  Receiver could remain deaf for 3 seconds. It was necessary to optimise the hang function to suit standard amatuer operations.

Hang time is reduced without impacting associated AGC circuitry in which it is integrated. 

In ISB ( independant sideband ) equipped receivers both A18 and the standard fitted A5 IF Audio Assembly will require modification. The hang time IC is a HEF4538B monostable multivibrator U10 and U5 respectively. It is triggered on during higher signal inputs and passes a delayed control signal to following AGC logic . The delay dependent on AGC speed setting. In the slow AGC mode additional logic is activated to give a much more complex behaviour. This behaviour in slow AGC suited RTTY fleet applications.  Additional ICs switch U10 and U5 time constants to match AGC speed settings.

The modification sets the recovery time to  0.5 second in the receiver "slow" AGC setting. SSB control was seen to be improved and allowed real time monitoring with the  receiver reproducing the local transmitter simultaneously without needing for RX muting. Receiver responds to 3uV signals from 100mv ones in 0.5 second.

If a ducking balanced 20 db attenuator pad is incorporated in the receiver audio  600 ohm lines, (the pad fitted as a  external network circuit to  amplifier driving shack remote speakers) ) (pad in circuit when in local tx mode)  then  real time monitoring is almost ideal without need for manual intervention of receiver volume control . Two speakers and amps are used in ISB modes . Car sound amplifiers were found most economic as audio amplifiers for these military receivers.  

The modification adds a 220k resistor fitted in parallel with existing 820K  R58 in A18 and R54 in the A5 assemblys. The resistors are fitted with PCBs installed . A Anti static strap is  worn grounded to the R 2368 chassis to avoid any static damage to the surrounding CMOS IC'S. Refer to R-2368 URR instruction manual download available elsewhere online. Publication 10215-0022B July 2015


Photo below shows: The Harris R-2368-URR receiver set up on test bench with A18 and A5 module covers removed  ready for modification. A anti static strap was  grounded to the chassis and used when working on the PCB cards as inatvertent contact with static sensitive chips was made during in situ in circuit soldering operations.















Photo below shows: A18 ISB if/audio assembly at rear and the A5 standard fitted IF/audio assembly in RHS  front. In ISB mode the A5 handles USB and the A18 becomes the LSB channel. The large blue dots indicate the areas where the 220K  1/4 watt resistors was added to the U10 and the U5 chip circuits. By looking closely the phillips cream coloured resistor can be seen close to the U10 and U5 chips.























Photo below shows: The method of adding the additional 220K  resistor  ( next to  U10 in this photo of the A18 assembly essentially piggy backing   R58,  820K  resistor) ( R54 820K in the A5 sssembly) . This is acheived  by first installing two vertical  pins then attaching the resistor seperately . This method was chosen to minimise damage to the PCB and allow quick change of test resistors during the optimisation process.

























29th November 2016: Test Equipment part and assemblys  sourcing and procurement for the repair of the shack instrument upgrade cluster was continued this month.  Search for service and operators manuals continued and reading them to familiarise with the instruments.

The need to aqquire a digital CRO developed and a selection was made that the TEK 400, 500 and 600 series was most interesting.  Two TDS460,s , a TDS520 and a TDS644A  were aqquired as e-scrap and one of these post repair will become the shack digital CRO. A HP logic analyser had been aqquired previously and it was found quite specialised and difficult to use. A 4 channel digital CRO was found to have a quick  set up as a 4 channel logic analyser to view a clock for sync and some  related waveforms simultaneously. With the trace records in memory unlimited time became available to analyse them.

30th October 2016. Test equipment upgrade:  A quantity of HP e-salvage test instruments disposed of as electronic scrap  purchased from USA and consolidated over period of 4 weeks to reduce shipping cost were delivered. If restored to serviceability would upgrade shack test equipment. Around 117 hours over the last month was spent on these. Some aspects of the work are detailed below .

Atvantage was taken of  the recent flood of circa 1984-87 HP RF Test Instrumentation ( Radio Frequency) ( gold series era)(aptly well named ) released to US surplus sales. Amongst these were a percentage of non working or incomplete units at  amatuer hobby prices (67 to 195 db) . A group of faulty instruments were purchased of same series, had readily available documentation ,and work was done to restore these. ( by module or assembly or parts interchangeability or basic fault finding). 

These were HP 8753A VNA, HP8753D VNA, HP8757A SNA , HP8643A Sig Gen, HP8642B Sig Gen , HP8622B Sig gen and HP 1660A logic analyser. Look up numbers elswhere for detail. A assembly line approach was taken and the group were assessed together given that lead times would be involved to aqquire repair parts and find manuals. All were deemed repairable except for HP8753D which will yield the directional couplers, APC-7 interface and solid state switch to homebrew a S parameters test set for the HP8753A VNA equivelent to HP8506A. Each unit was tagged with status and shortages. 

Photo below shows: HP 8753D VNA  (circa 1998) (vector network analyser) in progress of salvage of the tuneable YIG to use in the repair of the HP8753A (circa 1987) VNA. The  family of 8753 VNA analysers  use the same basic YIG. Earlier YIGs  have rounded corners and later YIGs have solid metal cubes. See repair of HP8753C entry 21 june 2016 for better photo of YIG. This commonality of interchangeable parts in HP8753 series VNAs is usefull when 8753 s are are aqquired as e-scrap. and use several instruments to create a useable one. Comments apply to hardware items. In the software , firmware and related PCBs  ( printed circuit boards), CPUs , interchange of RF front end samplers may not be possible. Refer to all related manuals.  

















The fault groups found were mainly switch mode power supply (SMPS) failures ,missing PCBs or modules, none locking PLL loops and  some attenuators missing ranges. Analogue faults were  more common then digital faults.  The HP1349A displays fitted to the 8757A and the 8753A  were missing one PCB and one had a low emission tube. 

Work was multiplexed to carry out repairs while searching for parts. A SMPS ( Switch Mode Power Supply) workshop was set up that restored functional operation to instruments. Considerable time was then spent on the cosmetic restoration . Good progress was made.

The  HP8643A was completed.  Replaces HP8640B . Being a contempory instrument displayed a fault list, the built in test diagnosis and routines made self repair possible . BITE ( built in test equipment) was used to locate hardware fault (PCB A6A2) . The  original PLL 2 test data was recalled from instrument memory and self calibration initiated to restore the failed PLL2 loop.    

The HP1660A was completed. (Replaces HP1600A) Initially the SMPS blew mains fuses on both 115 and 230 volt settings. Service methodology was to dismantle instrument and decan the SMPS to access component level . The  DVM diode test was used look for failed semiconductors on mains side. ( for later HP instruments SMPS schematics are not available.)  Then bench power the SMPS card with current limited supply and  DVM used to trace operation. The block sketch of the SMPS architecture was drawn up by observation helped. Care was taken to understand charge status of main filter electrolytic capacitors at all times.  

The SMPS was set up with a 40w incandescent bulb in series with mains active and this allowed a non destructive current to power up the supply so a voltage analysis could be made with fault present.  As repair progressed ( replaced shorted diode on load side) input current dropped to low level and lamp didnt drop any volts. This soft supply method allowed probing of the SMPS while fault is present.  

The HP8757A made useable with low emission tube the CRT filament voltage was raised by 1 volt by shorting out the series resistor in CRT filament  circuit . Made a noticeable improvement. Instrument useable . The HP8753A ( will replace HP8505A) has missing cards and is waiting on parts.  

Photo below shows: The HP8757A SNA ( scaler network analyser) in a bench test  set-up configuration. The  HP 1349A  Digital Display Module removed  and semi dismantled and connected and powered on for troubleshooting and  alignments of  primary and focus resolution test patterns. Adjustments of PCB A1 (PCB most visable on photo centre front).
























Photo below shows : The  HP8757A SNA  1349A  display A1 PCB which contains the deflection ampliers  undergoing troubleshooting for deflection  problem. The methodology was to compare closely two cards , one good and one faulty, after extensive testing did not reveal the exact faulty component.  The suspect IC was A1U29  1826-0871 ( price 200db) was listed ITAR and restricted  export from USA. So both ICs were unsoldered from the cards and augatt IC sockets installed . The faulty card could then be powered up and the good IC substituted for the suspect one. In this case the IC was OK and fault was open circuit  R87 X  1K gain pot. The IC s were both returned to original cards. The socket installations allowed  parts interchanges without impacting instrument build standard.























Photo below shows: A portion of the the HP8757A 1490 display A1 card with Augatt IC socket installed . Placing a socket in the target  repair area allowed considerable flexibility in the repair process. Can act as a  monitoring point and injection point for a source to verify in this case the following horizontal amp was OK, Finally when the original  part was re-installed the the quality standard required of the repair work was met. There was a big reduction on mechanical and heat stress to the IC from multiple soldering operations. 























The HP8642B (will replace HP8640B (close in testing) ) is useable and waiting on a attenuator workshop to restore missing range. Adjustments to correct  PLL 2 out of lock conditions were completed by following troubleshooting methods in service manual. The HP8622B SMPS was missing the A7A3 power supply  card otherewise complete.

The HP 8662A was completed,  (will replace HP8660B )The  replacement SMPS card A7A3 received heavy maintenence , the blown main switches HP part 1864-0657 NPN 73 watt were replaced with  Motorola 2N6308 transistors, Other components replaced were 5.2 v rail main electro C6(PCB A7A4) , Q3 and Q4 base fuses, 160 volt electros C1 and C2 and replaced along with instrument line fuse. One of the two main switch heatsinks missing was fabricated. The instrument had no other faults other then cosmetic  work.      

30th September 2016. Remote Receiver Site, Inclement weather has delayed work and progress at site slowed . Upper tower maintenence n such as replacing bird damage coax tail sections, rewrapping link yaggii joints with conformal tape was carried out. Field strength  test set is being prepared to carry out RF conducted and radiated measurements on the revised/ upgraded NBN wireless internet terminal equipments. On first impression there has been a significant reduction in EMI levels .The test results will be compared with earlier test data. 

26th August 2016. Progress on Collins 718U-5 HF 280,000 channel transceiver  system (100 watt SSB usb, lsb , cw, data, and ame)(28volt DC)  installation  for VW Kombi.  Final optimum configuration was determined as One radio shelf comprising  collins 671U-4A, 548S-5 and onboard homebrew test /maintenence set  located at whip antenna base itself ( 10 inches of hi Z unscreened RF strap  length inside vehicle) at rear of Kombi. Antenna whip is fed through  low stray capacitance hole of 5 inches diameter thru vehicle side filled with  teflon sheet circular plate.

Shelf electronics supported by remoted Collins 346B -3 audio control centre ( has speaker amplifier and microphone preamplifiers and compressor) (small ARINC standard rack )  and  Collins 514A-4 remote control head located in custom roof console near drivers head with  mike audio, speaker  and  RF power/SWR meter. The wiring loom and audio support for the 718U-5 system did require some thought , all looms and longer 4 metre ( 12 feet) sections are screened ( RG-214 coax  was stripped down and braid salvage and expanded and wires threaded through) . Connectors were used generously to allow looms and system to fabricated/ tested  away from vehicle and quickly installed. 

The basic radio shelf was designed and constructed, space was left for the test bench .The mounting  tray for  the 548S-5  amp coupler was designed and fabricated.  The Kombi mounting hardware was devised and installation into the Kombi is in progress . Waiting on 20-39S connectors from OS ( OverSeas) and loom wire in colour codes and mix of wire gauges and design in progress. The photos below show this work. 

Photo below shows: the basic components to create the homebrew radio shelf for the Collins 671-4A and 548S-5 to create the 718U-5 system.  The  LHS shows the  homebrew antenna interface  assembly for 548S-5 amp coupler. Note the antenna porclain insulator itself sits on a fibreglass panel and the thru metal hole is 50mm ( 2 inches ) in diameter  to reduce stray capacitance of the RF hi impedance path. 























Photo below shows:  the completed homebrew 548S-5 mounting tray . Several features were included in its design. Provision was made to allow switching to 50 ohm loads  for operational flexibility and ease of testing. A Jennings ceramic vacum relay was incorporated in the high impedance line. Configuration was disciplined to avoid stray capacitance , The type n connector can be seen . It is switched in by switch toggle visable on distant side of assembly rear. 

 Another design feature is adding some flexibility in bending of the rear assembly to aid locking in of the 548S-5 unit rear mounting ledge . By installing the  548S-5 box by inserting it at 45 degrees when fitting. This ensure positive location of the box itself  and aids pressure of mating connector strap to rear rf connector button on the 548S coupler.  A copper beryllium strap is used  as the pressure contact .























Photo below shows: Completed homebrew 718U-5 mounting shelf , space is left and reserved in foreground for additional system breakout connectors and test access items to be determined . The original collins 990C-3  radio set mounting for the collins 671U-4A is in the foreground. 





























Photo shows : rear view of homebrew 718U-5 radio system shelf . The main bendix connector is 20-39S but differs from the 20-39S connector on the front of the 548S-5 amp coupler  in that the orientation of the main DC pins pair are rotated 45 degrees. 
























Final configuration decided on is to fabricate a side mounted elevated radio platform at  rear of VW to meet 10 inches maximum length high impedance internal antenna wire  to 5 inch diameter feed through bush through vehicle side wall whip antenna element. Care is taken to minimise stray capacitance at all sections of the RF path from PA amplifier /coupler  to whip.  28V DC 20 amp power will be available at platform mounting point and Radio control will be mounted in overhead console near drivers head and fed with a 16 feet loom extension from the rear mounted platform. . 

Photo below shows: The loaded homebrew 718U-5 Radio shelf fitted to the VW Kombi. Care was taken to ensure adequate mechanical strength of this mounting configuration. 























Photo below shows: Rear view of the VW kombi mounted homebrew 718U -5 radio platform with installation work in progress. The Harris CU-2397/G antenna coupler in the RHS foreground  will share the same whip as the  100watt 548S-5 coupler. Switching will be with a high voltage jennings glass vacum relay.  The 500 watt harris CU-2397 is used if a linear is needed . 



























23rd July 2016.  Collins 671U-4A aqquisition of supporting hardware and installation circuitry was pursued this month. main consideration is the physical formatting of the radio system in the VW Kombi and the technical support strategy. Example: create a separate test bench or add the the test bench into the VW install itself.  Other considerations is should the 718U-5 system be installed as removeable shelf with everything on board including a test panel with lamps and test points  points excluding the remoted 514A-5 control head. 

To gain best efficiency from the 548S-5A amplifier coupler it seems the 718U-5 system needs to be distributed to allow the maximum of 10 inches of internal hot antenna lead to antenna base from the rear of the 548S-5A inbuilt coupler. 

The test bench can be added to the receiver  exciter 671U-4A shelf  and the loom feed to the normally distant 548S-5A can brought to the shelf by adding extra connector sets to allow re-location of the 548S for testing  on a 172H-8 antenna simulator. 

21st June 2016: Maintenence and repair of shack test equipment continued this last month. A HP8620C sweeper and HP8753C vector network analyser were repaired. Further  work was done in designing a test wiring loom for the Collins 671U-4A HF radio. It was decided to fabricate a breakout rear terminal board to allow access to connections and become test points and attach this to the rear of the radio. 

Photo below shows:  HP8620C microwave sweeper during service for missing +5 volt supply. The 8620 was non functioning. Measureing at test points on  A4 and A5 powers supply cards showed  blown fuse  on 40volt  and no +5volt and fan not working. A module extender was cut-up  and  A5 card extended  for DVM tests. A shorted  Q8  SCR crowbar was  replaced and useing 3A silver plated wire mended the plug in ceramic on board fuse F2.



















Photo below shows: HP 8753C Vector Network Analyser under repair for no stimulus source RF output  and a broken front panel type N connector due to a analyser  drop on corner. The repair of the damaged RHS type n connector is made easier by the HP design which allows the RHS control panel to be removed. The RF connectors bracket panel was straightened ( assembly is shown on bench centre ) and semi rigid hardline re- fabricated to original matched length. 


















Photo below shows : The faulty A3 source assembly removed from the HP8753C and semi dismantled to access the faulty tuneable YIG (  shown in foreground). It is possible extend the cables to the YIG and relocate the A3 assembly into the 8753 mainframe ( the ribbon cable is long enough) and use DVM and CRO to test YIGs voltages and sweep drive signals. The YIG is then located free and sits adjacent to top of the the A3 assembly with terminal card fully accessible.  The YIG connects by flexible coax to its original A3 port.  

The YIG can be directly connected to a Spectrum analyser ( +12dbm YIG output) to measure its output.  If its needed to test the remainder of the A3 assembly stages  Simply connect a external oscillator to LO 3.8 to 6.8 GHz port ( see this in port photo below) via  the flexible coax that was used to the extended YIG output. Terminate the YIG with a 50 ohm SMA termination when ever YIG is powered and not under test. 

























Photo below shows : The Collins 671U-4A HF Receiver Exciter homebrew breakout terminal board that mounts on rear of the radio and recieves all the wires from the adjacent  main 150 pin rear connector.  Top and bottom conects are primary 24 volt supply. The other groupings are for Antenna Coupler, Radio control  and Linear Amplifier . Around 44 wires are required. to also accomodate the TGC and ALC test networks. Any additional potentiometers or circuitry will be on a sub board mounted directly above this one. The commisioning of the radio will be simplified by having easy access for measurements and monitoring control functions. This system is fully automatic when PTT operatedmomentarily. Since the linear interface and amplifier will be homebrewed





























18th May 2016: JW Miller AT-2500 Semi Automatic Antenna Tuner repair : Inservice with VK2BLC in VW Kombi since 2006 the costant use of manual tuneing which overides DC positioning motor wore out the gearbox and required replacement. A search found these motor and gearbox assemblys are used in coin operated machines and one vendor  (tsiny.motor.com) was chosen that had the right physical dimensions and higher RPM units available. Unit used was 12.5rpm, this would be the minimum and recommend 50 rpm if one can be found. This allows the manual operation to overide the motor.

Photo below shows: The JW Miller AT-2500 antenna tuner and useing two 12 volt DC motors as servos to complete automatic tuneing when inductor tap switch tap is correctly chosen. These motors are fitted at rear of insulated tuneing capacitors. This confined space doesnt allow many other replacement options  
























Some work will be required to prepare the tstiny motor for installation as its rotating shaft while correct diameter is longer 

Photo below shows: The tsiny motor on left hand side set back by spacers and ready for installation . The setback is needed to allow suficient spacing from the tuneing capacitor and avoid RF voltage flashover. There is a forked clip under the motor which has to moved back by same height of spacers chosen.. 
























Photo below shows : Completed installation of RHS rear DC motor gearbox assembly useing the 12.5 RPM version . This does require a reasonable effort to turn manually but is possible. Chose a higher RPM if one can be found. 
























27th April 2016:  VW Kombi Radio System Upgrade  is in progress and will use the Rockwell Collins AN/ARC-174 ( 671U-4A) HF 0.4 watt, all mode 28,000 channel transceiver. The refurbishment of the VW Kombi 28 volt electrical system was completed which has as its central key component a 40 AH Marathon 20 cell Nickel Cadmium battery.  The new configuration will reduce the reliance on AC power in the Kombi.

The remote receiver site commissioning is on hold untill NBN solve their interference problems.  

24th March 2016: The  Remote Monitor Control panel  ( RMCP) for the remote receiver site rack was homebrewed useing salvaged HP metalwork. The concept  and value of recycled HP cases has been mentioned before. Can reduce build times and produce a better result.  The RRSR ( Remote Receiver Site Rack ) equipments were assembled on a development rack to speed up loom and wiring harness design.Simultaneously the circuit design for the RMCP is emerging from the functional block since this unit needs a full understanding of the entire rack system. Its function is to control power and test and monitor audio circuits.  In design, less is more and in the custom build  process of a once only build the exact wiring connections and circuit type can vary. At the end of the process the generation of documentation is the most important to contain the fine detail .To preserve the build and generate the system instruction manual .  Project planning useing the GANTT bar type tools can help where there are a number of tasks going on at same time. 

Photo below shows : The usefullness of Hewlet Packard  salvage metalwork to simplify home projects . The problem  faced here is the front panel has  many holes.A new dress panel was made, Exisiting holes were used if possible. Panel  major items were moved around gain a useable ergonomic layout. (Given the conflict cuased by existing panel )























Photo below shows:  The completed RMCP front panel useing recyled parts . A low cost labelling machine was used with 6mm tapes  to obtain the scaling down of the font size. 12 mm white on black tape used for larger equipment headings. Flat black spray on paint was used as panel background.  The general white on black panel lettering theme is to provide a match to the Collins HF-80 Receiver. In link systems audio levels are extremely important. The VU meter is special kind of meter with fast ballistics which enable it to indicate audio magnitudes in real time. Here the meter is standardised to +4DBm is equal to O VU.  The meter high impedance does not load the 600 ohm  balanced circuits which are used extensively. It is used here because of its fit for purpose and simplicity.Both uplink ,downlink, signaling , levels can be monitored.  














29th February 2016: Construction of a purpose applied electronic workshop to develop the control and equipment racks for the remote receiver was completed  Work involved fabrication of test bench, and test equipment shelving with a capability of  200KGs ( 420lbs)  as HP  instruments average out at 25 Kg's each  and two stacks of four is quite possible. All timber construction was used along with bolts to allow complete flat packing at later date. Finish was flat black paint for structural parts, Jarrah wood stains on 5 ply plywood and carpet felt squares for bench surface. 

Photo below left shows:  The development rack fabricated from U section mild steel to hold one set of  link equipments under development and ease of design and fabrication of the electrical and RF looms and Krone termination panels configurations. Once design is complete these will be  re-installed  in the on site electronics cabinent. Wheels are fitted to allow quick rotation and mobility of the rack. 
























Photo above right shows: Remote receiver site development rack loaded with rack units in preparation to design the wiring looms and position Krone and terminal blocks allow the rack system interfaces to be created. 

26th January  2016: Collins AN/PRC-47 repair. A transportable more powerful HF radio was needed for recent trip, A PRC-47 was selected for its extensive CES  ( complete equipment schedule) which gives it considerable operational flexibility . The  47 set was taken out of storage where it had been for 10 years and made servicable. On test the radio failed to transmit or receive. The service methodoligy for this radio is mentioned below.

Photo below shows: The 47 set after diagnosing problems and prior to the repair work . One pair of 2N2287 transistors for the powers supply ( centre front) and the no go amplifier modulator module. A homebrew antenna port adapter top LHS was used to simplify test equipment connection..  






















Before the intitial powering  a visual inspection of the 47 was made and the 20 amp fuse was found to be blown .( indicating faulty switching transistor failure Q1 and Q2). It was replaced with 5 amp fuse to limit fault currents for test purposes.A DVM was used in diode test mode to check the  suspect transistors. (the base leads  were unsoldered first). After the replacement of the transistors the 5 amp fuse was sufficient to allow most testing. Once repairs were  completed and radio working the 20 amp fuse was replaced and the final testing of the PA amplifier at 100 watts can be carried out . 

Photo below shows: The location of Q1 and Q2, the 2N2287 PNP germanium devices that were replaced as a pair. Refer to manual TM 11-5820-509-35 November  1974. Some 47 sets Q1 and Q2 are fitted with copper heat spreader. New heat sink grease was applied to devices. 




































Photo below shows: Additional test suppoort items. 100watt 50 ohm 30 db attenuator plus 20 type n attenuator allows direct connection to Spectrum analyser (TX) and to HP signal generators (RX) without fear of damaging if 47 set is operated on transmit. ( the output of the HP8640B is simply increased by the 50 db to compensate a direct connection. A motorola fist mike with internal amplifier card to work as alternative to standard 47 set carbon mike. A compact 34AH 24Volt aircraft sealed lead acid  gelly battery to replace the standard silver zinc battery. 
















Photo below shows : The module extender kit special tools, Collins ( cable assembly set AN/PRA-4) which contains transmitter output test unit  as per the manual. The option used by VK2BLC of the homebrew adapter and 30 db attenuator system to supplement this kit is also possible. 




























AN/PRC-47 Receiver serviceing notes:   To quickly test the receiver power was applied. On first observation the RX was no go, there was no noise present. The 47 was set to 7 mhz and the HP 8640B applied directly to the  PRC-47 antenna port and RF output set at -20 dbm. A signal could be heard and this allowed the synthesiser to be tested and was found normal and on frequency. It was also noticed the warm up behaviour of the tubes in the front end increased the receive level with elapsed time. That cleared the data signal translator of being suspect. The fault was lack of receiver gain, it was very deaf. 

Check  was made of the  power supply module TP (test point) J7 for 24v and  J8 for 20 V to verify receiver supply voltages . The HP8640B was set to an output of -50dbm and applied to the antenna insulator,  The overall receiver signal path was divided midway ( by troubleshooting convention)  by selecting the  amplifier modulator module for testing .The module was connected to the extender lead and set out as below . 

Useing the CRO and 10:1 probe measure RF signal at J3(500KHz in ) then look for amplified version at J1 (500KHz IF amp output. It was found much less in this radio . Transistors DC operating voltages were checked . A DVM was used to measure volts at R21 (power to to Q2) and similiar voltage at R26 (supplys Q3) and found low at R23 (3volts) instead of around 12 volts.  Measurement of Q3 emitter to ground showed 0 volts indicating shorted 2N274.  

Photo below shows:  The amplifier modulator post repair and Q3  2N274 germanium PNP small signal transistor that was replaced in the LHS lower corner of the module. Refer to the module cover for parts location. Two other amplifier modulator modules held as spares were found to have  problems with the 2N274 transistors.( shorted emitter collector junctions). They had been working OK before storage so recommend seeking out a few 2N274 transistor spares. 

The transistor was replaced , signal alignment carried out and shared transmitter path tested.Power supply +AGC TPJ16 was near 7 volts and receiver noise quite active. Sensitivity improved from -50 DBm to -103 DBm or near 2 uV  for 12 db S+N/N. Transmit output was then tested and found normal.

The module was also fitted with 500 KHZ  USB mechanical filter to convert the radio to LSB for  80 and 40 metre use.
























Photo below shows:  the quality build and repairability of this radio, notably the extensive component and assembly markings easily cross matched to the manual for troubleshooting and performance based alignments ad the printed component layouts on module covers.  

































28th December 2015: Station Maintenence, Collins AN-TRC-75, power amplifier stock/spare tubes, testing.  The  4CX250R 7580W  external anode PA tubes require periodic powering to keep in useable condition. This was carried out and at same time  newly aqquired tubes were tested. The test method is mentioned below.Those good ones previously tested are simply plugged in and run for 5 minutes at at least 100 watts average output .

Photo below shows: The AN/TRC-75 T-730 HF RF power amplifier was adapted as a test bed for 4CX series tubes . The GRM-10 test perspex bench cabinet RHS and the TS-1325 /TRC-75 ramp test set LHS form the tube tester. Several modifications are made to the  T-730. A  1/4 inch access hole is drilled thru a cover directly over R91 bias potentiometer which allows the sectional cover to be refitted to preserve air flow integrity. The 4CX tube spring retaining clips discarded temporarily. This arrangement allows quick acces to tubes under test during matching process.Air is supplied from  the GRM-10 test bench blower. Interlocks operate when perspex lid is raised. Tube anodes are shorted momentarily by external means before physical removal. Test points of individual tube anode current and screen balancing divider switches access is a rear end of T-730. Other voltages and currents are available at the feedthrough set under front cover. These are analogues of the real voltages and currents and are scaled to to read correctly with Fluke DVMs and AVO  8's . Refer manual . 
























The aim of the process is to prevent tubes from gassing up and keep them healthy . At same time test any newly aqquired tubes. They will be tested for  low emission, noisy, and gassy ( will short when HV applied) . Note that  tubes prior 1967 were tested with a current limited ionisation tester  to 2.5KV between anode and cathode without filaments alight. Voltage is raised till tube flashes over, then repeated , each time the flashover volts will increase untill the required 2.5 KV is reached .  If the tube cannot be coerced to required voltage it was rejected. 

Tubes are run up with filament for five  minutes then static bias set at 87 mA per tube and HV applied to the group three chosen . Same manufacturer were kept together. This is a test position available on the TS1325. eg T1 static bias , In this position balancing can be carried out or value just recorded on tube. Other 1325 test positions  such as T2 tune power , T3 full  suite of AGC , AM  TGC  TGC , RF output power and sidetone . T4, T5 and T6 are spot frequencys thru bands testing power output.  These are the typical ramp tests for a TRC 75 radio set.  

For the tube evaluation a different apparoach was used . Only T4 position on the TS1325 was used after static bias is set . A HP8640B RF signal generator is set to 5 MHz and used up to +20dbm  which substitutes for T-730  drive from the TS1325 to T-730  BNC input connecter. after auto tune up iscomplete. A 1KW power meter and dummy load substitute for  the TS1325 dummy load. RF Drive level is controlled and all tubes currents can be seen. 

The plate current is monitored at C100 feedthru on front panel T-730 , Individual plate currents at T-730 rear. Correct pushbutton pressed to PTT system and drive power is varied from 10 dbm thru 20 dbm ( 1kw average at 1320 mA) . The observations are made of  PA current behaviour  and stability and a monitor receiver is set to AM and tuned to amp to listen for tube noise such as ragged irregular static. Tubes are usually well behaved and  many ones aqquired at low cost may not have power capability. They are simply low emsission.  300 mA plate current capability is required for reosanable output powers. The occassional one will trip the overcurrent or fail to produce any current at all.  

Photo below shows:  A closer view of the T-730 shows the bias potentiometer R91 which is located LHS upper chassis qudrant centre . Ths needs to readily accessible as mentioned in text. It is possible to test the tube by moving the bias voltage to look at the higher current capability of the tube under test and plotting  the characteristic cuve. The tubes should be rested between measurements.   



















30 November 2015:  Power supplies, batteries, antenna systems maintenence.  Station maintenence of infrastructure in progress, full safety inspections of antennas and mast above and below ground , retensioning and greasing .. 

Main station 24 volt battery banks have been load tested for voltage drop and capacity. One  330AH cell Yuasa UXL series 2Volt cell was replaced which had cracked case. The Yuasa UXL in-service battery bank  resistance was measured at 15 milliohms including interconnecting straps and cables.These were built from out of date UPS (uninteruptible power supply) cells in 2006. Were originally manufactured in 2001.

The VW Kombi main SAFT 24V 36AH nickel cadmium  battery was refurbished , Refurbishment basically re-balances the 20 cells, tops up the electrolyte ,tests the capacity for a 1 hour rate. Two cells were replaced for  high self discharge current. See photo below. 

Photo below shows: The main VW Kombi SAFT sintered nickel cadmium surplus aircraft battery following refurbishement.  Nickel Cadmium batteries have been in service in the Kombi since 1978 . These compact batteries can yield 1300 amperes  for 50% voltage drop for 10 seconds without damage. In service of turbine starting they are expected to suppy an average of 700 amperes for 40 seconds. They drop 0.6 volt from open circuit voltage of 25.2V to maintain greater then 24.6 volts for 100 ampere load. The weight is 80lbs (34 Kgs) and lifetime is over 40 years in amatuer service since battery is  fully repairable. Main atvantage is they can be left in discharged condition without damage.  These batteries have very low scrap value compared with lead and cost less to aqquire as surplus item.

Previously sourced from defence surplus, general aviation has stopped useing these in favour of the sealed lead acid battery making them more available. Typical drop in sealed lead acid replacement now used in aviation is the "Concorde" with a service life of two years.

For mobile operations of  high power SSB amplifiers the sintered plate nickel cadmium battery offers the highest energy density and lowest internal resistance at the lowest cost and physical size. Matches well with SSB battery demands. It is always assumed a charge value of 30 amps is available and the the battery recharges in the receive mode  balanceing  the average power removed in the transmit cycle. The internal resistance of this battery was measured at 7.5 milli ohms.  To put his into perspective. A premium battery group tof Yuasu UXL 330AH  (amp hours) taking up 6 times the space and weighing 240KGs  (500lbs) internal resistance is 15 milliohms.

The aircraft Elcon quick release mating connector unit can be difficult to obtain , it was found the large socket pins from the Amphenol 32-5S panel mounted socket ( blue plastic insert type, held in by circlip ) can be removed and fit the male terminals ( see below in photo )  of the battery to fabricate connecting cables.  

The individual SAFT cells use raised threaded bolts and nuts. The Marathon type use tapped holes and allen screws.






















The photo below shows : The group of fans in use in association with the Collins AN/TRC-75 .

The high flow, high pressure Siemens regenerative blower (LHS) This was dismantled and refurbished . This blower cools the AN/TRC-75 and supplys air from a remote outdoor cabinet via 3 metres (10 ft) of 50mm diameter tube ( 2 inches).

The blue Rotron( RHS)  is a very usefull smaller version regenerative type , Also 230 volt single phase 50/60 Hz . Could cool the TRC-75 easily in the 400 watt RF output range . This is used in the GRM-10 test bench in lieu of the 400 HZ noisy type.

The black wrinkle Collins Vaneaxial blower in the front is a 400Hz 12,000 RPM is a similiar type  to that used in the standard TRC-75 which has two fitted. This one is part of the AN/GRM -10 test bench.

The siemens blower (LHS) is single phase 230 volt ac , 745 watts and is the most suitable premium blower for external anode tubes when the cooling air supply is a long distance for noise or other reasons from amplier.  Can be used in both suction and pressure modes. The performance is 2.89 PSI in pressure, 629 Torrs of  vacum, 154 cu ft min. It is vibration free and has a low noise level of 57dbA .

























22nd October 2015: Maintenence and repair of shack instruments continues. Work this month was done to improve shack test and repair facilities. The aim was to reduce instrument clutter to more high utilisation group.  The use of older instruments will always need more bench space due to their restricted test and measurement frequency bandwidths compared to the later instruments.   

Photo below shows: Reconfigured instrument and homebrew test assembly and circuit board repair area. Most commonly used instruments are in this cluster. The layout general trend is  RF analysis to LHS, RF souces to the RHS, Monitoring and most commonly used general instruments to centre. Extra collapsible camping sourced tables are added when more layout space is needed .Distance of test cables is not excessive since impedances are mostly 50 ohms. For probing high impedance RF circuits a HP 85024A rf probe is used in conjunction with the HP8560A spectrum anlayser centre mid shelf. Use is made of simple wooden but strong racking ex Ikea. Power circuits are zoned to one kept alive all times for frequency counters and remainder are switched via earth leakage circuit breaker in three groups. The  photo shows a HP8640B under repair . 



















30th September 2015:  HP8640 RF Signal Generator repairs. A9 Peak Deviation  and Range Switch Assembly. A1 RF Vernier Assembly.  While homebrew resources stocktake and test equipment assessments is still continueing. Four HP  8640B Rf signal generators used in the shack since 1998 were repaired.

Some filtering of the ongoing homebrew  projects was needed as the parts and assemblys needed to complete them  are still ongoing and  to decide a resonable time frame for those that can proceed. 

The remote receiver site still has considerable field time input requirement to complete by christmas. Notwithstanding solving the NBN noise issue. This project moves forward. 

Bench construction mini projects , 400/600 watt Harris cut down RF-1110A RF Amplifier for VW and the  100 mW to 80 watt HF-80 series exciters interface to generic power amplifiers  are still waiting for development. Assemblys, parts and metalwork are still being consolidated. These mini projects move back and will each use a GGant bar time line.  

One development has been to replace the extensively used fruit and polystyrene boxes with removeable lids with see through plastic storage bins , 25 litre , 45 litre and 55 litre types which now have become low cost.

Projects useing  military surplus equipment parts and assemblys are now trending more difficult to plan as sources are patchy and more scarce  which means open time lines. Places more emphasis on project managment ( in a normally  informal ham domain) and preserving ,documentation and  identification is necessary untill all parts are in hand. The bins are good for this application. 

There is a 2BLC shack trend now to salvage equipments and assemblys more then before to obtain key parts  and remainder discarded as storage space is now a premium. Often it is far more cost effective then seeking individual parts.

The aim is that in the end by having the unique parts for homebrew modifications to Collins or Harris surplus equipments if undertaken can be fairly indistinguishable from the manufacturers build culture and appearance. Military systems tend to use the same parts through many cycles of equipments over a 10 year slot. In the domestic of commercial  electronics they lack this standardisation. 

HP 8640B RF Signal Generator Repair 

Some instruments to be kept for long term were selected from the test equipment pool for maintenence and repair.  A working  bee on HP8640B's was carried out . These signal generators have the high spectral purity capability needed for high performance tests on SSB linear systems. They are the only HP RF sig gen capable of  +20 dbm  (100mW) ) RF output . All Collins Rockwell  and Harris RF power amplifiers  require a 100mW (+20 dbm)  drive level  and for this reason they  are considered  significant shack assett. Various functions do fail in these over time, however the main problems are well within the scope of ham repair.   

A minimum of three HP8640 signal generators are required for intermodulation and other receiver tests. These instruments have a high usage in the shack. Four HP8640 units had accumulated faults all related to the same assembly. 

Three HP8640  rf signal generators all had  faults in same FM deviation control assembly, There was  no FM modulation and incorrect meter scale lamp indication.       One HP8640 display did not indicate the correct band frequency when bandswitch was operated.  These functions were all controlled by the  A9 Peak Deviation and Range Switch Assembly.

All four instruments had lost small contacts from the clear plastic programming disks present on these switch assemblys. These assemblys failure were considered to be age related since and the plastic spigots retaining the contacts had broken free. Serviceable complete repair assemblys in working condition were not found so a repair methodology was devised.  

These dropped contacts easily get lost  during the process of removeing the covers to fault find. Only 4 of the 12 contacts missing were found in the case. 

It is necessary to salvage from obsolete HP instruments to a low cost source of these contacts.  The ideal instrument to salvage these contacts from was found to be the  HP data error analyser HP1645A . See the photos below.

Photo below shows the desired repair part required ,This is the universal switch contact used extensively throughout the HP8640. Used in the FM range bandswitch A9 assembly and the RF Attenuator assembly. The source of this contact is the HP1645A instrument. ( and others) .


















Photo below shows HP1645 with module being salvaged to obtain the small contacts usedin the HP8640B repair 


















Photo below shows the source switch from the HP1645A from which the contacts are salvaged. The switches were easily removed and contacts salvaged. Notice HP must use special tool to cap the plastic spigots to retain the contacts. This is the target standard to be aimed for when fitting the contacts to the A9 plastic disk spigots. 




























After retreiving the contacts from salvaged HP 1645A near 20 contacts were obtained. The HP8640  A9 Assembly was removed for service. The HP8640 service manual procedure was followed. Setting the band switch to 16-32MHz range was found to help lift out the A9 when the variable audio frequency oscillator is fitted. Task involved , setting switch positioning for assembly removal, removeing knobs, shaft retaining nuts and  DIL connectors .

 Photo below shows: The A9 assembly partially dismantled with clear plastic programming disks with these contacts  that can fall away visable. Refer to the HP manual for the disaassembly and assembly instructions.

 A cracked gear  is visable in the photo. Not all cracked plastic gears need to be replaced. The super glue used to glue mirrors to car windscreens is ideal to repair  these gears. Refer to the windscreen specialist for correct effective use and use a clamp to close the gap during the fast set process.  The superglue is a two part. One part applied to each side of the cracked gear. When the clamp closed the split in the gears the adhesive goes off in 20 seconds. 

























Photo below shows: The two disks after repair. It was noticed there were another set of good plastic contact mounting spigots on the plastic disk, the replacement contacts were fitted to these new mount areas. A soldering iron tip was used to melt a small retaining cap on the spigots ( or hot glue gun with fine tip).  The repaired disk is then rotated 180 degrees to the new alignment position. Notice in photo there are two white teflon disc buttons. These have to be transferred to other side opposite the newly  fitted contacts. In the photo this has not been done. Became aware later not all contacts visable were required and some  may require removal. Refer to HP manual. At time there was no gold assembly to copy.
























Photo below shows: The other set of mounting spigots that can be used to repair the programming disks visable on the left. Refer to text. Also visable is a view of a good set of contacts almost correctly installed. Notice one contact not aligned fully. 
























The A9 assembly took a little concentration to master the dismantling procedure  and retreive the discs prior repair. The HP service manual had clear instructions. Most essential was  the alignment of the programming disks during re-assembly . The front two discs will have the contacts pointing directly down and the rear disk will have the disc with contacts vertically upwards. When both switch shafts are fully rotated CCW. Refer to manual. The assembly was found to be quite complicated and a marking pen was used to index all moving parts to frame as reference. 

HP8640B Rf Signal Generator Repair A1 Vernier Assembly . One of the signal generators had no RF output and fault tracing showed an open circuit in the rf power vernier cicuit which involves the clear  programming disk fitted to the attenuator rear. The attenuator  assembly was removed and close inspection showed all contacts broken free on the clear disc and they had no contact pressure. Work was carried out to repair the disk . 

Photo below shows: A1 Vernier Assembly dismantled , The programming disk with repair completed ready for  re-assembly.
























Photo below shows on left hand side (LHS) where original contacts broke free. On the RHS the unused set of spigots on which the contacts will be assembled . The teflon buttons are moved to the opposite side . A Weller temperature controlled iron set at 300 deg F was used to collapse spigots and in the case where contacts were still loose  a fine amount of hot glue was used .





















Photo below shows: completed repair on the disc before re-assembly
























31 August 2015: Instrument and Resources Stocktake. While inclement wet and cold weather contiues a full stocktake of test intruments is in progress including extenders, documentation and service aids. Test equipment groups are separated by general frequency band of equipments under test and equip the test bench  . If microwave task is in progress then those instruments and service support items are retreived from holding area. Generally the division is , VLF , HF , Microwave , Audio groups . Aim is to avoid test bench clutter. 

30 July 2015: Repair of HP 8660B synthesised signal generator . While inclement weather prevents general field ham projects more test equipment has been repaired indoors. The HP8660B sig generator is a high end plug in based high resolution source with 3 parts in 10 to 8th internal standard   and 1hz settability from10 KHz to 1300MHz.  These  instruments have been appearing in quantity as surplus and the usual fault is non locking of output frequency.

There are a number of nested phase lock loops where the outputs become combined. Work was to align two unlocking loops. Module extenders or test cables are not required for work on these fold out loop module areas.  The sig generator is relatively complex and requires the service manual. There is a another supplementary manual called  "Service Manual" "8660A,8660B,8660C Synthesised Signal Generator System" which contains a compilation of typical faults and good group of technical photos of entire module set and block diagrams. A small training period was  needed to understand the loop adjustment procedures. The procedure to offsett the reference voltage VS the DAC voltage for certain calibration dial frequencies presented a small skill roadblock. Since it was repeated  for each  loop it became easier.  

Basically there are end point VCO DC voltages to set, and then recentre the actual DAC ( digital analogue converter) decoded voltages to produce precision set VCO output frequencies. The actual voltage is needed to fall within a acceptable error  to allow the loop to lock reliably. Various pots ( multitude) were  accessible with alignment tools thru access holes in the modules. A standard 10:1 CRO probe was used with high impedance input frequency counter.  All test points are on the large A2 mother board related to the loops and were accessible . Refer to manual.   

HP 86632B Modulation section AM and FM HP 8660b plug in module Repair. 

This module had no modulation output on AM and FM and HP8660 was off frequency with FM selected when plugged into the mainframe.  A HP11672A module extender kit was used to  allow the module to be extended from the mainframe. The service process adopted was to familarise with the block diagram and note the test point architecture . The module was extended to the test bench, all covers removed, mainframe energised  and DC operating voltages checked. A oscilloscope was used to track the modulation frequencies through the module. It was found the A4 Leveling Amplifier PCB had no audio output. The DC leveling DC control voltage on  TP1was seen to be wrong.

The fault was the failure of the R14 variable gain control device. This consists of a 5V mini lamp and photosensitive resistor in a D crystal type case. A resistive measurement of the lamp filament was made in circuit and showed lamp open circuit. 

Photo below shows: The  A4 PCB (centre ) removed  from the HP 86632b plug in. In foreground of the A4 PCB itself it is possible to see what appears to be a D type crystal . This is the R14 opto resistive  gain control device mentioned in the text. 

















The R14 assembly was desoldered and opened with side cutters around the lower beaded edge to asess repairability. Uses a leaded 2mm 5 volt bulb with cold resistance of 8 ohms DC. The small bulb was carfefully replaced and mated optically to correct position. by adjusting lamp connecting leads. The assembly was assembled and package glued togethter with araldite around lower edge.  After replacement the AF output was calibrated by A4R35 as per manual. A extender board was used during trouble shooting however adjustments are accessible without requiring extender. 

HP 86632B Modulation Section off frequency in FM mode.  The calibration button CF fails to aqquire correct centre frequency.  The module uses a free running VCO correctible 20MHz oscillator for generating FM modulation. This was found to be out of alignment . The full VCO Frequency adjustment was  seen to be tedious , in this case the procedure was shortened to NOT involve the select component on test.  It will be necessary to set the HP 8660B sig gen to exactly 10MHz and use a high quality counter on the RF output. Follow the manual procedure but use the mainframe itself as the frequency monitor . Note the 20 MHz oscillator cover has a huge impact on the set frequency , so that was taken into account when setting the free running frequency. When pressing th CF button with fm selected but no modulation the sig gen RF output will be seen to zero itself onto precisely 10MHz, then when cal cycle complete will slowly drift away to some error. This error has to agree with the manual at 5 seconds later. . 

Photo below shows: The 86632B modulation section extended from the HP 8660B mainframe and A4 Leveling Amplifer extended for trouble shooting. Various test equipment is connected. The HP 3325B signal source( top left)  with 10KHz test signal generator applied to module input. The TEK 2246 CRO  ( left lower ) connected to the A4 PCB AF output . The HP141T spectrum analyser with  8335B plug in displaying HP 8660 sig gen under test RF output at 30 MHz (top right). Fluke 77 DVM for measureing DC control voltages. This set up was used as the 86632B test bench.




























25th June 2015: NBN generated RF interference at the remote receiver site. The recently commissioned rural NBN home internet service that replaced the previous broadband wireless service is creating severe radio interference at the remote receiver site and needs to be resolved . It will come down to system design issues over double insulated switch mode power supplies in NBN equipments without any earthing provisions and plastic enclosures enclosing high speed data equipments with out sheilding or RF bypassing of interfacing cables.    Ham projects have been affected this month to get this matter up and investigated.

 The 300 watt Harris HF linear amp project is waiting on suitable metalwork and assembly positions redesign to create a 19 inch version of original homebrew design. A 22 inch enclosure system was originally put together. A rethink was made on this non standard width  and considered it would lead to practical problems in the later operation and deployment options of the amplifier. 

27th May 2015: VW 1974 Kombi Radio Platform engine failure: Radio  projects were put on hold when the Kombi suffered  a serious engine failure requiring immeidiate attention. Most ham operations involve the Kombi. To avoid a complete engine stripdown a Technique to remove cylinders heads without removing engine was developed.  This was accomplished ,however the operations may be more time intensive then removeing the engine alone.

Whilst stalled at traffic lights and continous cranking to get started there were two loud engine internal explosions.  Tests revealed no compression on cylinder three for 1800 cc type 4 engine. The valve gear was stuck open by foriegn material and required attention to the inlet valve and seat. Work was carried out in the confines of a car parking spot. Note this was for LHS of engine. After engine repairs it became apparent the cause was intermittant spark from the ignition coil due HV insulation failure.

Photo below shows: basic tempory workshop for task. Remove no 3 cylinder head and repair inlet valve.Sitting on the chair is the the oil cooler duct/bracket that is main difficulty in removing the LHS cylinder head. The text refers to this problem.






















Pre preparation to access the cylinder head.

In brief , raise van another 12 inches, position engine at number one compression. , Remove LHS engine sealing strip,remove air cleaner and carburettors and note their electrical connections, and accelerator cable and throttle bar.  Remove HV harness, and distributor , mark rotor position . Plug all openings with paper towel as they appear.  Remove oil pressure sender, plug sender hole, Remove muffler , remove heat exchanger. Remove following tin work,  three LHS pieces, The centre rear piece Will be neceasary to disconnect  vacum, fuel pipes.Remove screws from RHS tin work to allow centre metal work to be lifted free. Remove LHS main engine air ducting tinwork cover. The cylinders will be visable. Remove rocker cover , rocker gear , pushrods , tubes retaining spring , pushrod tubes( use plastic pockets and remember where each push rod came from) ( same with rocker gear). Remove tinwork under cylinders,  Remove in reverse of  tightening order the cyl head bolts.     

This part is where the problem getting number 4 cylinder free is overcome, remove oil filter, loosen alternator and remove belt , remove air blower fan cover and remove blower fan ,loosen cable of air duct warm up flaps control shaft, remove screws attaching blower main housing and pull assembly LHS outward. This will allow some clearance to allow the heavy tinwork bracket that ducts air to the oil cooler . This a juggle but the bracket will come out.


Photo below shows: LHS head removed , No 3 is LHS and No 4 to the right .The bracket that causes the problem of releasing the cylinder head sits above the oil cooler and requires the blower fan housing assembly to be pulled rearwards. See text  Once oil cooler duct /bracket is removed the cylinder head can easily be removed in vehicle.






















After cylinder head repair make sure all the important surfaces are clean. Use  rolls royce non setting jointing compound on all barrel to crankcase shims and surfaces by moving cylinders forward . Then rotate engine and do the other cylinder. Move barrels in position to avoid touching the long head bolts.Fit the heads and tighten head nuts in order (refer manual) . Juggle the filter duct bracket back into position and fit up all the cylinder and head assembly airflow control  tinwork Reverse assemble all assemblys starting with positioning the main blower housing. Fit up the blower and cover and  timing scale. Assemble in reverse order all tasks and use a pointed rod to help locate the holes in the tinwork to get screws into. Reset the engine to top dead centre on No 1 cylinder and refit distributor with rotor towards  distributor cap port No 1 lead connection  port . Check the valve tappett clearance. ( 4 thou inlet and 6 thou exhaust).

Helps when dismantling groups of assemblies to place different sets of screws in plastic bags and mark them with their location. Once engine is running use timing light for ease of getting timing right ( vac hose to distributor off and 7.5 dgress before TDC.)( auto transmission)


29th April 2015: Test equipment repairs , reconcilliation of of parts on order : While waiting for parts and fabrication items for Harris 300 watt amplifier project,  repairs and maintenence were carried on HP test equipments sourced as salvage and unrepairable. HP 8660B /8632A/86603A RF signal generator combination , The DCU and pushbutton front panel assembly  was completly replaced and the A22 frequency doubler  was trouble shot and repaired in the 86603A.

HP89410A VSA, vector baseband analyser, now obsolete: no go, power supply (PS) A90 was trouble shot and repaired. PS outputs were interlocked, repairing + 15V restored all voltages. HP9440A frequency converter , recovered from scrap : was trouble shot and repaired for failure of A82 40MHz buffer. Units were then mated up and serial data cables fabricated. Combination then became a HP 89430A 1.8GHZ VSA. Once operational all cosmetic works completed.

Photo below shows the recovered  HP 89410A VSA after placed in service. The display unit is fundamentally a 10 MHz dual channel IF baseband analyser coupled to a RF downconverter .  These early instruments are now commercially obsolete and  are usefull in amatuer service. Main application is testing and measureing, dynamic time and frequency domain signal behaviour, digital signal phase performance, transmitter spectral purity, VFO transient frequency pulling on PTT, Complex RF signals can recorded direct from antenna or dummy load sampler and saved in hard drive and replayed thru internal signal generator as required for analysing their signal parameters and transients at later time.  3 dimensional displays are available. The waterfall with graphical multiple time variant frequency traces ( frequency, time , magnitude all expressed in numerics with calibrated cursors ). The spectrographic in a colour display format with colour representing magnitude as shown othe HP89410A below. The LHS coloured bar ranges in red ( 0dbm )to blue (-100dbm).  Time is displayed vertically and frequency horizontally. The orange vertical line is the 936 MHz CW signal at -10 dbm. The vertical white line is the moveable marker. If connected to a antenna a whole complex of dashes of colour and lines will be observed. This display type can pick up and characterise ssb tx splatter. An ideal instrument to examine SDR transceiver transmitter digital modes performance. 

























Currently being used to support understanding of digital modes tests,  performance assessment and aiding repairs to a Harris RF-3466A 39 tone doppler shift corrected HF 1,200 bauds modem.

Schomandl SND 500S, recovered from write off:  500 MHz synthesiser, no RF output, found all minicircuits ERA 8 SM broadband amp MMIC 's had lost gain, all same batch number ,other batch numbers OK, replaced 5 MMICs in the RF DSP frequency platform. 

23 March 2015: Rhode and Schwarz HX002 Antenna coupler antenna combination: Work was done to configure and check BITE (built in test equipment )functionality of the HX002 multi element dipole HF antenna coupler system. Aim was to familiarise with the HX002  and assess suitability for use in the Remote Receiver Site. 28V DC operated, capable of operation and automatic tuneing without need for RF power to tune. Ruggedised for remote unattended operation and frequency agile. The unit can decode serial data to set operating frequencies in less then 60 mS. MTBF is 10,500 hours. EMP surge protection quoted to 50KV/m >5nS pulse. 

Photo below shows: The HX002 during electrical testing after long storage.


















Photo below shows  the  HX002 during functional configuration to application, The HX002 is arranged in a vertical physical sandwich stack. From top down, antenna element mount head and RF EMP protector , matching network,  balance to unbalance RF transfomer ,switching elements and blower and lower  EMP Protection, control unit electronics compartment and EMP filters.   


















Photo below shows CPU module removed and being configured for operating mode boundaries and data speeds up to 2400bps. The Junction unit GX007 left hand side can be 180 metres away and allows BITE testing on demand, fault supervision , status lamps, manual control and interfaces to transmitters and computer. This coupler can hot switch RF at high speed. 


















Photo below shows: electronics compartment, from left to right , attenuator,measurement module, CPU module (removed), Driver Module ,Power supply module , in front lower the filter board 


















Photo below shows the HX002 RF network tuneing engine. 32 by 28V DC motors drive the fibreglass push rods in both directions .  

































Photo below shows the HX002 high speed RF switches. The plungers move vertically to contact circular gold plated petals  
























23 February 2015: Harris 300 watt HF RF Amplifier: Parts aqquisition still in progress, design not finalised if needed to design around available assemblys.  

30th January 2015: VW Kombi Radio Platform Harris 300 watt HF RF Amplifier mini project : Kitting and aqquisition of components in progress. Design problems in the metalwork fabrication under consideration.  To keep the Harris chassis roll out concept or fall back on removing panels for access. 

22 December 2014: Additional work long distance MF Receiving antenna, Multiplexing an antenna design :

A number of MF antenna types had been constructed to continue to maintain broadcast listening against  increasing noise levels. The block ferrite antenna was satisfactory but picked up the magnetic switching fields from the stations own solar system which rendered it ineffective. The 5KVA inverter was fitted with low pass filters and had no effect.

The wire antennas picked switching hash and other noise from neighbouring solar systems  BUT WERE free from  noise from the stations own inverter. It was concluded loop ferrites antennas responded to the magnetic field vectors  and wires didnt.

The discovery that stray switched magnetic fields with a rate change of MF frequencies had a significant range suggests a concept to design a transceiver working on magnetic fields alone.   They could induce currents into loaded circuits and loops. Were difficult to supress as magnetic sheilding was required.

Once this was identified a solution was designed. The general MF electric noise in a wire is was found to be prortional to wire length. A short conductor would be required. The 20 metre antenna was mounted highest point in the station and well clear of any objects. Would lend itself to multiplexing frequency bands.

The one element 20 metre antenna was redesigned to work simultaneously on both 873 KHz  and 14.2MHz. The 2GB level was 10uv and the 873 KHz noise level was 20uV. The concept was to use a ferrite that had a large permeability at 0.5 MHz of over 200 and falling quickly to a permeability of 10 or less at 14MHz . It would not be lossy but just frequency sensitive.

The iron powder balun core was replaced with ferrite. The 20 metre dipole element was helicaly wound on fibreglass and the stray capacitance increase was then exploited for  a series resonance  of low Q at 873 KHz. The 20 metre resonance was obtained on shortened elements and a secondary response near 1MHz obtained . The short horizontal sections on 873KHz produced a acceptable MF signal to noise ratio and could drive 100 metres of UR67, 20 meter match was under 1.5:1 over 250 KHz  was still obtained .

It was necessary to design a switching panel to steer the MF signal when 20 metres not in use . At same time the ancillary RF panel could serve other functions.

The desired result of not picking any of the inverter magnetic switching fields was acheived for mums 2GB long distance receiver allowing the  the ham shacks solar system to power the shack full time. 

Photo below shows: RF  ancilliarys panel components before fabrication.





















Photo below shows: Assembled RF Ancilliarys Panel. The MF sharing of the 20 metre antenna uses a coaxial relay  that switches to 20 metre operation when 20 metre is selected and drops of the MF feed. Other functions added are a grounded mounting for the Bird thruline sensor element and a high voltage attenuator to limit signal to the AM modulation monitor while the AM capability of the station is being developed. Dulux flat black spray paint is used to create panel and white on black labels applied
















Photo below shows the dominant connections for the Dow Key coaxial relay


















Photo below shows : RF ancilliarys Panel installed in shack



















13 November 2014. Remote Receiver site link duplexer : The installation of the outdoor 2 metre duplexer was completed.The duplexer is used on the 2 metre yaggii link antenna to the remote hf receiver site. The homebrew duplexer was developed useing recycled components and optimised over time. The cavity flter group was fitted into a recycled switchboard cabinent. The outdoor cabinet  was reformatted for the application.

Photo below shows: Basic earthworks to allow cable access and installation of paver slabs as suitable mounting surface for the steel base of the cabinent Tacky wrap sheet ot Denso grease impregnated tape for steel protection can be used under the cabinent to reduce corrosion . 

























Photos below show completed outdoor duplexer installation 

















































Photo below shows: Treatment of the lower mast area for the VHF cables , The addition of the small block fence  prevents whipper snippers from cutting into earths and coaxes. The pebbles over black pastic prevents grass invading this area .
























03 November 2014. Long distance MF reception: Experiments were carried out to test a block of ferrite as a basis for MF antenna in a noisy environment of surrounding multiple solar systems. A reference antenna of a loaded 40 feet sloping wire was matched to 50 ohms . The MF station chosen was 2GB Sydney 873 KHz .The path was 400kms ( 300 miles)  and signal recovered from ground wave was 10uV. The interference level was 20 uV.  A block of ferrite   12 by 2 by 1.25 inches was wound with differing number of turns and to reduce the temperature sensitivity due to very high Q was set with a reduced number of turns and resonated with near 380 pf . Match was set at 25 db S[2:2] or return loss. The final result was 8uv of signal and a noise reduction  of 20 dbV was acheived side by side with sloping wire. This improved signal to noise ratio would benifit a receiver if a ferrite block antenna was used on 1.8 Mhz or 500KHz and splitting the receive and transmit antennas. 

The final tests of completed antenna prior installation were . Bandwidth : 7KHz , S[2.2]: 25db at Fo at 873Khz and -3db points. , Rejection of local noise field:  20 db , Mounting  height 10 metres, Impedance : 50 ohm , Signal level recovered ground wave from 2GB : 8uV.

Photo below shows:  Final optimised form of homebrew block ferrite antenna .The antenna element shown is inserted in a dogbone shape of storm water 90 mm plastic pipe and mounted at height. 















Photo below shows: the completed rolling pin or dogbone radome  section for the ferrite block insert









Photo below shows: complete antenna assembly , Far cap can be removed to adjust exact centre frequency , Jointing sections are wound with conformal rubber tape just prior to installation after final adjustment with dogbone attached to side of step ladder. Return loss is adjusted to 25 db or better at operating frequency .  











16th October 2014. Remote Collins HF-80  Receiver Site: Work is underway to install coaxial and control cables to the feedpoint of the broadband receiving array. A number of cable access pillars along route are being fabricated . A elevated cabinet at antenna feedpoint initially be almost empty as the LDF-450 converts to feeder tails. Provision is made for future RF antenna switches to allow site expansion .

Photo below shows earthworks right of way waiting for laying in of cable groups. 































17th September 2014. VW Kombi Harris Radio Platform revised : RF-1110A Amplifier , The amplifier has been removed to make way for a rebuilt simplified version . Basically the Harris RF1110A is being cut down to one 300 watt modules and standard set of RF1110A module series to support it.The revamped amplifier system will lose the entire RF-1124 power supply , 3 PA modules, the high power low pass filter , and 19 inch wide fan blower. All the rest will be reassembled in smaller case and powered by a generation 4 1KW SMPS 50V smart supply, size 4.5 inches 10 inches by 2 inches and weighs just 2.5 lbs.The replacement LPF filter will be used from the 350 series Harris transceivers. The amplifier will look in colour and design exactly like a small brother of its larger parent. Mini project expected to be complete  by June 30 2015.The benifit will be a amplifier more suited to Kombi application. Design concepts and block stucture for new wiring loom and parts list has been made. Metalwork fabrication has been commenced .

21st August 2014. VW Kombi radio platform engine refinements.    Engine repairs were completed  and engine installed along with improved instrumentation useing avionics surplus sensors and instruments.  A new plug HV lead sheilding system was designed and fabricated as screened plugs now only available to defence  users. New high pressure oil lines were  fabricated to allow remote located oil pressure transducer , new cylinder head thermister sensors in design process to allow dual head temp sense.  Will use threaded holes in head bodies rather then under spark plug thermocouple washers. Overhaul 14V alternator.

The high voltage sheilding for the standard ignition cables utilises the silver plated screening  removed from RG214 coaxial cable. The outer screen is threaded over the standard HV lead and secured in place with heat shrink. Connecting tails of screen sheild are retained and leave the screened cable just before arrival at the spark plug connector. A mounting post is installed at each plug location and 6mm screw attaches the screen. At the disributor all 5 tails have crimped lugs and these bolt onto the side of the distributor at one point.  A quick receiving test shows this lessoned method of screening is adequate to reduce ignition noise.

Photos below show: LHS shows completed engine installation after heavy maintainence and the RHS shows engine bay with engine removed. Note the break out boxes on firewall equipped with cannon connectors which receive the engine screened wiring harnesses .



















Photo below shows: The modified VW ignition system, The fully screened ignition system has been replaced with a screened system useing standard VW spark plugs.   There are some small length sections not entirely screened . The suppressed coil was retained and HV connection standardised. Also visable is the additional 28 volt  30 amp Neihoff alternator with homebrew mounting bracket assembly with attached regulator. The drive pulley is one supplied for driving airconditioner compressor. Here it is used to drive second alternator.
























19th July 2014. VW Kombi radio platform engine repair. Sourcing of required repair parts, welding and machining of crankcases, cleaning and painting tin work, basic re-assembly bottom end

24th June 2014. VW Kombi radio platform refurbishment.  Inclement weather, cold  temperatures and short days are slowing progress.





















Photo above shows: Kombi motor crankcase during teardown to access camshaft
























Photo above shows: 1800cc type 4 engine new camshaft being fitted , the stripped teeth can be seen missing on the old camshaft  in photo centre.


20th May 2014. VW Kombi radio platform. The vehicle is undergoing heavy maintenence to original engine which has 277,000kms. Has broken camshaft.





















Photo above: mechanical work shares some commonality with homebrew radio set construction , the sense of building 


23rd April 2014 Collins AN/MRC-95 Antenna Coupler 490B-1 Installation and homebrew Remote Control Unit.


As an alternative to cutting down a tree that was sheilding a general all band antenna it was decided to relocate the end fed wire antenna to new location and utilise the antenna coupler system taken from collins AN/MRC-95 vehicular radio group. The trunk mounted 490B-1 antenna coupler was a completly self contained coupler suiting this application. A Remote Control was designed to allow use with generic transmitters.

The 490B-1 collins coupler system was chosen since it was sealed against insect invasion, splashproof , had 1KW average power rating, covered a full impedance range, used a very common aircraft coupler series 180R-X ( 1958 -1968). Has internal cooling fan when used at 3 MHz at power.

Typical final tuned VSWR for all frequencies on a 60 ft wire with 1 metre cage top hat was 1.2:1 or better. Coupler limits is 12 amps RF current or 5KV. Blower fan is designed to remove 70 watts of heat from loading inductor at 20 deg C .

Photo below shows: Remote control (RCU) under construction. The front panel layout is based on function, front panel controls are moved around obtain the best layout and clearance with components underneath.


























Photo below shows homebrew RCU assemblys layed out in configuration allowing future servicing and changes before assembly.Wiring is arranged in common paths to form a wiring loom and laced with lacing cord

























Photo below shows: Completed collins 490B-1 generic remote control

























Photo below shows: Collins 180R-6 antenna coupler interior after replacement of the ceramic drum tap assembly and fitting of new 500pf vacum capacitor. Refurbishment of the ceramic drum rollers and brown fibre tap rollers was required. The new tap rollers are made of different material.



















Photo below shows: Internal layout of 490B-1 antenna coupler. 180R coupler support electronics are two servo amps, sequence controller, not visable underneath module platform are 400hz square wave to sine wave filter , receive antenna changeover coaxial relay that transfers connects Rx coax line from direct antenna to to tuned output of coupling network.

























































Photo above shows: Cabling to the 490B-1. Coupler can be internally connected so only one feeder is needed for both Rx and Tx.

Photo below shows the wall mounting and RF installation of the 490b-1 trunk. Note the claw clamps concept used in the jeep installation is carried over to this installation to avoid the need to puncture the trunk cabinet with any mounting holes. The cabinent is well sealed against moisture ingress.
























04th April 2014 Rerfurbishment of CSA surplus "longshot" half rhombic HF broadband antenna.

One task this month was the restoration of a CSA longshot antenna kit , this surplus kit had damaged winding reels , knotted mass of wires and missing termination.

Work was to reconstitute the plastic reels with fibreglass and homebrew a 370 ohm in line antenna leg broadband termination. To simplify the unravelling of the knotted wire mass the various wingnut plate joined sections where the kevlar centred braided copper wire joined through was cut and rejoined again after the entanglement was removed.

To reconstruct the reel all the broken pieces are re-attached with superglue to regain the form. Prior fibreglassing the chopped glass fibre sheet was first trimmed as a circular piece then halved. Some reel sides were missing fragments were ignored as holes were filled later. The fibreglass resin was then brushed on and chopped sheet shaped to reel rungs. See photo below.
























The excess fibreglass was trimmed around the reel circumference just after the fibreglass set. The other side of the reel was repaired also. After 12 hours curing a orbital sander was used to produce good finish and then flat black paint was applied. Then reel reassembled.

A new termination was homebrewed using a network of heat sunk non-inductive low cost ceramic flat film 50 watt resistors. The original design of the CSA termination was preserved.

Photo below shows the ventilated casing of the termination under construction.















Photo below shows: The homebrewed assembly parts of the termination before assembly. Note the vishay non inductive resistors on the heatsink. Space is left for a larger group if higher power is required











Photo below shows completed broadband termination. Impedance test showed the ac impedance as 356 -J20 ohms at 30 MHz. DC resistance value of the Vishay fat film resistors was 345 ohms. It is expected the antenna would be rated 400 watt PEP with termination. This type of termination can be used with any standard wire in conjuction with a matching transformer to create a broadband antenna.

























14th March 2014, Heavy maintenence on Collins AN/TRC-75, R-761/ ARC-58 receiver exciters.

This month was spent on the repair of failed TRC-75 modules. GRM-10 test bench was set up for the repair and alignment of three 465B synthesiser modules . See photo below. The 465B module consists of precision coarse and fine servo positioning for 4000 spot frequencies and further a 24,000 electronically generated ones in two electronic control loops , Mechanical positioning brings the freq to within 3KHz .The coarse electronic brings the 3KHz to less then 400 Hz error , then the fine phase loop reduces the error to that of the reference frequency standard in about 20 seconds.The RF output originates in a stabilised master oscillator of high spectral purity.

Recovery of 465B modules from R-761 receiver exciters from long storage.

These modules came from long storage and failed to lock to frequency. A manual was required to locate and identify modules and assemblys. Hints that follow are a guide to the service methodology based on the work to get these units serviceable.

Methodology was to first verify R-761 receiver exciter under test was feeding ramp freqs and voltages and mechanical drive to CV465B systhesiser module. Then testing the 465B module for known output freq and see it lock. If not then a few hints on what to do .

The R-761 rx was used as the test bed itself. The R761 was warmed up 5 minutes and when commanded by control C-3141 to several frequencies and observed 465 and 1528 module racks move freely.

(1) Checks of ramp frequencies were made with CRO and AM1522 servo amp (DVM) are necessary. Check SG179 standard output on CV466 module 100KHz ( 5v PP ) on J1, 4KHZ (4vPP) on J2 ans 1KHz (4V PP )on J3. Check SG179 2.4MHz output (5V PP) on AM1529 J1. Check for RF output on AM1529 J2(6VPP) ( set C-3141 freq 15,700KHz).

(2) Check of servo amplifier AM1522 with DVM ac range, connect DVM across J2 and J3 and set a new freq into 3141. should be around 38 volt indicating normal motor drive voltage then decrease to 6-8 volts as servo stops moving.

(3) Basic check of 465 module locking was made used main test points of interest TP A2J2 on top edge of A2 card assembly, was shorted and unshorted to ground to check locking. Set C-3141 to 3,716 Khz. Connect CRO to top of RF can test point marked J13 near small tuneing rack, this TP monitors main module RF output. (3V PP) 2 to 4 Mhz. Connect frequency counter to J13 and frequency should be 2,006 Khz exactly (if locked) . Ground A2J2 with small wander lead and note freq should be 2,006 + or minus 1KHz .Lifting the A2J2 short should see the freq zoom back to 2,006 khz precisely.

(4) Listening to locking behaviour was found useful. Connect a synthesised signal generator to R-761 rx input BNC and feed RX with -50dbm at 3,712 Khz. Set 3141 to LSB , Listen for lock after C-3141 freq set to 3,712KHz. within 20 seconds and hear it go to zero beat. set C-3141 control to 3,713KHz and hear 1Khz note. Then 3,714Khz and 2Khz note.Can set USB and set 3141 to 3,711Khz to hear locking lower side The way the note personality establishes gives an idea of how healthy the synthesiser is . If no lock behaviour module needs attention.

(5) The most common problem found was the drift in the relationship of the precise mechanical positioning to SMO output frequency.

The SMO (stabilised master oscillator) frequency 3,006Khz at J13 (C-3141 set to 5,716Khz) should coincide with the null of the follow up servo pots measured at J10. (less then 10mV) A further null occurs as the IPO tunes and a null of less then 10mV should be seen on J11. See the manual for detail and will need module extender , a long spline key, ACmV meter with differential input to reduce common mode stray 400hz pickup. Carefull with locking collars when loosened.

(6) The alignment of A2 IF amplifier discrimminator circuit card was needed in all 3 synthesisers .

The sensitivity of the T1 and T2 cores to physical drift will make this alignment necessary as second most cause of non locking of CV465B module. Refer to manual for procedure , fabrication of aluminium ground plane. See photo bleow . Synthesised signal generator will help for fractional frequencies around 455KHz.

Very little problem was found with any circuit components due to the high quality of the build. Levels and waveforms were little affected by ageing . However the locking ability had to do with the interaction of the electrical and physical alignments that set precise frequency windows.

Photo below Shows the most important 465B circuit card, the A2 IF sub assembly set-up and under alignment. Two test jig items were fabricated to improve the alignment process. Top RHS module is a plug in probe replacing the A3 IF mixers subassembly to allow injection of the IF test signal. A component network as per manual has been added to prevent the A2 card from self oscillating. The RHS of module shows the aluminium mounting to provide a ground plane for the A2 IF amplifiers circuit board .Without this the A2 card is unstable.

The work on the A2 card is carried out after the mechanical positioning alignments , SMO (stabilised master oscillator ) tracking corrections are applied and IPO ( interpolation oscillator) frequency alignments are completed.

At the bottom of this bio the A2 card is shown in test position in the Collins AN/URM-124 test set. 




























Photo below shows: A section of the AN/GRM-21 GRM-10 test bench , the 465B synthesiser extended from its AN/TRC-75, R-761/ARC-58 receiver exciter From LHS clockwise , the Collins R-761 upside down , AVO 8 used to indicate DC tuneing trends when aligning frequency discrimminator L1 and L2, the octupus box which drives the R-761and makes available primary test access when performance testing, the AC millivoltmeter used to carry out servo system alignments and measure servo error voltages, typically under 5mV during mechanical nulling, the C-3141 control head ,the 465B as the device under test.
























Photo below shows: Items in the radio test set group AN/GRM-10. Items 2, 7, 12 , and 16 were used for the tasks above. Use of 1 is optional in cool temperatures.  Photo extracted from Radio set AN/ARC-58 handbook field maintenence instructions. T.O. 12R2-2ARC58-2. Publication date: 1 May 1958






















17th February 2014 , Design , fabrication and installation ham shack Solar power system .

With removal of the need for three phase mains supply with the 400Hz now sourced from DC . The complete shack power supply systems have been redesigned. A solar stand alone system was designed and built from recycled assemblies to generate 50 units of mains power per week.

For just the one only cost of 3 kw hours at 33 cent kwh can purchase 1 watt of photvoltaic power with 20 year life. A solar power system was designed with target performance of 9 units per day based on system loss overall of 30 % . Panels were chosen with a optimum knee at 30 volts at 8.16 amps and a nominal system charge voltage of 27.6V. Choosing this panel voltage allows direct use of high current 24 volts for military radios if needed.

Use was made of MPPT control to optimise power extracted away from the main part of the day.Tests of solar tails 17volt or 3A panel currents could up convert to 27volts to maintain battery charging. DC to DC converters were chosen for modification to regulators. A dual 24 volt input configuration was chosen and outputs in series to upconvert to 54volt. A recycled 5KVA American Power Conversion matrix 5000 sine wave 48Volt DC inverter was supported by surplus Hawker Energy SB110 6 volt cells to make up a 220 AH 48V battery bank. The role of the battery bank is more as a dynamic stabiliser during high inverter peak loads.

A 70 amp 1,000 volt EMI filter was designed to reduce inverter and switching and clock noises from being radiated by the solar panel wiring and array in the broadcast band. A target of -50 dbc in 550 to 1600KHz was obtained in conjuction with daisy chains of earthing with respect for single point grounds.

Switchboards , Termination boxes , PV panel concentrator box , 2,000 watt regulator , EMI filter and metering and supervsion equipments were all homebrewed from recycled components with only a small number of new components . The 50mm DC wiring was sourced from recycle. A 7 day programmable timer was used to control solar from mains changeover .

Some consideration that impacted the design was the need build a extra low voltage DC system that allowed home construction and firefighters to fight the home fire if one were to occurr.

The photos that follow show the final system .

Photo below shows : The individual panel concentrator termination 12 by 250 watt panels and providing hardware interface to 50 mm squared copper cable.
























Photo below shows: Homebrew 2,000 watt MPPT solar regulator made up of a parallell series combination of 500 watt DC to DC converters. The plus and minus 24 volt rails are monitored by individual ammeters and the voltmeter indicates the regulator output voltage .


























Photo below shows : The use of recycled items , the DIN rail connector blocks , terminal blocks , surplus panel lamps, aluminium and perspex. The labelling is useing P touch labeller with white on black tapes.
























Photo below shows: The homebrew broadcast band EMI filter rated at 70 amps useing 30 yellow ferrite toroids and 10 uf mylar block capacitors to obtain 1,000 volt rating to match the PV panels rating. The filter is inserted between the regulator and the DC cables to the solar panel array. Dirty signals enter from left hand side .























Photo below shows: The almost completed solar power open plan system. From top LHS in clockwise direction , the 2,000 watt MPPT regulator, the PV panels isolating switch and 75mV DC shunts , the AC metered sub board with AC inverter isolating switch , the 48 V preservation battery charger to maintain cell condition when system layed up , the DC switchboard with battery bank selector and circuit breakers and including DC supervision to protect batteries against over- discharge damage.





















Photo below shows : The use of the the PV concentrator box installed . The inputs are the individual panels . The two panels side by side form the plus and minus 24 volt pair . Panels connected vertically dont produce as much output as paired units horizontaly under practical conditions. The output of the array leaves on a 3 wire differential circuit . The zero volt line is also the earth.






















Photo below shows: The final installed array. Space is left as vertical coridor to allow maintainence or faulty panels to be replaced more readily The panels are slid sideways to allow access. The mounting rails are not cutoff at array edges for this reason.























Photo below shows :Typical rail extrusion and roof mounting bracket . Note rubber washer under bracket to minimise cathodic corrosion . Mounting system makes use of TEK roofing screws.
























Photo below shows: The solar power system tie in with the residential supply under construction. The solar system connection  format is the same as that for emergency power changeover. The selected loads are either connected to mains or solar power. The ham shack power circuit is selected while other residential loads remain assigned to normal supply.  In the case of loss of mains power, emergency power can be made available to domestic supply. The  changeover homebrew sub-module is top board centre. Protection of electricians is by board mounted  inverter supply isolation switch. A  programmable smart time switch controls the changeover to solar power. 


























17th January 2014 AN/TRC-75 support systems and radio maintenence.

Full load testing of the 75 set on the Avionics Instruments Inc DC to AC 3KVA static inverter at temperatures to 40 degrees C and full loads showed no degradation of radio performance , some changes were made to the interlocking of the 75 set against loss of cooling air and corresponding shutdown of inverter. Performance tests showed inverter AC output well regulated with 24 volts source voltage. The original USA AN/MRC-87 , AN/MRC-83 system PP2352 inverter requires greater the 26 DC input volts to maintain AC voltage regulation to drive TRC-75 to full power and is difficult to run off 24 volt batteries.


20th December 2013 , Collins TRC-75 400Hz power generation and control system upgrade.

A mini project completed this month was to to phase out the Bucknell 5KVA 3 phase 400Hz rotary gen set previously powering the Collins TRC 75 and upgrade the power source to a 3 phase 3KVA 400Hz solid state sine inverter system. Primary power for the 3 KVA inverters is 27.6 Volt DC at 138 amps. When useing ex aircraft inverters it should be noted they may not contain overload protection and startup contactors . Task involved the fabrication of a Inverter Shelf that contains all the necessary DC control , Metering and interfacing and providing remote startup circuitry.

Photo below: shows basic modified reworked metalwork from recycled sources






















Metalwork is by far the most time consuming and after drilling and bending final finishes are applied

Photo below : shows completed shelf , the design is indicative of the necesary functions to support a high current surplus derived solid state inverter. Note the use of a surplus aircraft load meter. These meters are 50mV, driven from current shunt and adjusted to read 1.0 when inverter is at 100% of its capacity or drawing 138 amps DC. A different approach to outright current displays. Night lighting is utilised as a benifit in useing ex aircraft instruments. Panel is finished in flat black paint and lettering is by P-Touch labelling system of White on Black.

















Photo below: shows another view and the application of a 150 amp DC high current aircraft relay. Anderson high current hamorphraditic DC connectors are use for quick release. A 200 ampere HRC fuse protects the shelf and inverter circuit.























Photo below : Shows homebrew  shelf fitted with late model 3KVA 1A3000-1A-190 three phase sine wave inverter and installed in application.  This inverter is the primary power supply for the AN/TRC-75 transceiver. 

Not quite fully visable underneath 1A3000 28V DC inverter  is the now redundant homebrew cabinet and electrical interface that duplicated the original collins AN/MRC-87 vehicular mounted cabinet. The cabinet contains the original PP-2352 2.5KVA  inverter which has its internal view photo near the bottom of this bio.(see 9th June 2007)  The 2352 has some interesting features. Regulation control technology in the 2352 is based on saturable magnetics.

Notice on the lower LHS the rows of LEDS and selector switch. This switch tests every power transistor in all three plus one phases . If any LED lights  that indicates a blown device. As the number of failed devices rises the operating modes can be adjusted to suit available power. There are over 38 internal fuses .  Another feature is there are three square phase outputs  for the blowers and power amplifier and one filtered sine wave output phase for the receiver/ exciter and  servo systems of the antenna coupler. 
























Inverter system remote Control

The inverter shelf required a Remote control unit (RCU) for operators position mounting to monitor AC parameters and alow remote switching of inverter.


Photo below : Shows homebrew RCU fabricated into recycled ex Navy cabinent . It is worthwhile to collect nondescript metalwork cabinents to stockpile and apply to projects as required to save on project time . Unusual Hewlett Packard instruments such as bit error test sets , are a good source of 2 RU cases and short 3RU cases. They are a inexpensive and useful to strip out and use as cabinets for ham projects. HP instruments from 1984 to 1990 embody unitised and flexible configurable hardware pieces components and can create a high standard in homebrew finish.




















Photo below: Shows rear interior of the RCU. The aircraft surplus instruments are easily terminated using connector pins only and heatshrink to lesson the need for the special instrument connectors .




























Photo below : Shows RCU installed in shack with night illumination on . Most airline surplus cockpit instruments internal lighting use 5V for interior dial lamps.


























Photo below: Shows upper above rack location of the RCU in the relatively small ergonomic space.Green coloured instrument top RHS is the PEP wattmeter. Control head on right controls the remotely located Collins tuneable band pass filter.



































Control System Upgrade

To simplify the operating requirements to bring all remotely located powers supplys and cooling air online for the TRC-75 system , the control system was redsesigned with a few key areas foucused on. That is all power, cooling sources are present before the TRC75 is switched on. All other support desk , rack and monitoring equipments are up . Interlocks and alarms are armed .

Various concepts were borrowed from aviation , the master switch and electrical DC and AC buss configurations , Submarine indicator panel design in the use of the visual "christmas tree " status display prior to dive. The simplified number concept to help operators perform the sequential startup in which dependent control operations are performed in right order .

Photo below : Shows the ham station control panel detail . The switch on sequence is numbered 1 thru 5 to bring all DC and AC systems on line and power up all equipments and cooling air. Progress from LHS to RHS . On completion of the process all equipments are available.

The lamps christmas tree panel centre top must have all lamps up in the row before the Collins an/trc-75 can be turned on.

Other functions controlled are antenna selection and which transmitter is on air and which transmitter is on dummy load , the selector switch is towards RHS .

Far RHS and numbered 5 is the rotary 5KVA rotary gen-set push button and status controls.














17 th November 2013 : STR-8212 Digital Receiver Restoration and Comparison with Harris RF-590 and Collins HF-8050A in SSB mode.

Work this month was spent constructing a working 8212 from three radios. The STR-8212 is a stand alone digitally implemented radio useing a 16 bit CMOS microprocessor control and VLSI DSP software algorithms carry out channel synthesis ,filtering , demodulation and AGC function. The radio is modular with 19 of both digital cards and shelded RF modules useing DIN series connectors for cards and combination D series mixed contacts for modules.

Photo below shows: the  STC model STR-8212 HF communications  receiver with top cover removed  


















In absence of technical manual , Service methodology established power supply , microcontroller system serviced first enabling the built in diagnostics (BITE). Selected cards were interchanged noting and matching software version and PCB revision lettering noting BITE errors dropping away and interpreting behaviour. Static protection for PCB's was implemented continously when handling all digital cards. The final modules last to be compared were the RF ones once the synthesiser was up. Eventually all 19 BITE tests passed. Correct function was verified for sensitivity, large signal handling and band pass channel filter behaviour. 15 band pass filters are available. Other performance tests were defferred .

Photo below shows: The rear view of the STR 8212 showing extensive interface capability particularly the Optic fibre transceive ports marked digital.



















Some observations were made about about possible faults. The receiver radio operates at high internal temperature and cabinent cooling needs to be correct . If the Receiver is operated with lower cabinent holes blocked the RX will fail in under 30 minutes at 30 deg C. Two micro boards had one tantulum each shorted. Use a DVM to find . The DIN edge connectors need more current wetting and BITE tests will fail. Cards should always be removed and reseated as most basic service procedure besides observing all the power supply LED indicators are green.

The receiever was placed into service and compared with both Harris 590 and Collins HF-8050A all running simultaneously off one multicoupler. A external audio amp and speaker were used on the 8212 as the inbuilt speaker is so small . Other then ergonomic issues related to the 8212 RF performance was almost identical for sensitivity and noise in SSB mode for weak signals. The digital receiver was not quieter. For digital modes that may be different but not tested. When the usual mix of signal levels for Ham nets were observed sometimes the 8212 surged with bursts of receiver noise. In terms of AGC control the Harris was ranked best (Slow AGC speed selected) , Collins second and 8212 third.

The range of filter bandwidths of the 8212 helped receiver in noisy local power derived interference situations . SSB when set at 2.4 KHz or even 1.2 KHz was available. Clarity was sacrificed with improved readability. Normal bandwidths are 2.7 KHz and 3.0KHz. The receiver was noted as free of internal spurious signals when listening to itself. If there were low down.

The 8212 is a very compact 2RU height unit , Some tuning hysteresis was noted when quickly cruising and the spin wheel could be weighted and semi- braked to improve ergonomics. The reciever offers a large number of control options.

As a stand alone front panel operated receiver it lacks the operating ease and display size found in the Harris RF-590 receiver. If driven from a computer with mouse and on-screen graphics that would take it into a different world. The receiver has control interface in both optic fibre and RS232 serial communications.

John Denby in UK was able to source a 8212 manual and made it possible to commence servicing of the faulty modules which differ from the normal analogue cards.?

23rd October 2013 Collins-Rockwell HF-8050 , HF-8054, HF-8010, HF-8014, HF80 Series Synthesiser Reference Oscillator Modules Repair. Four synthesisers reference modules were repaired, 3 had out of tolerance 9.9 MHz crystals with C1 at limits . One had shorted tantulum.

A compensation method was devised for out of tolerance 9.9 MHz Reference Oscillators that can no longer be adjusted to frequency with C1. Useing factory range of values for C4 and C3 will no longer compensate centre frequency to correct value . An assumption is made that the temperature compensation curve established by alignment of R1 and R3 is unique to the fitted crystal. Suggesting it may more desireable to padd the xtal and not to alter the temp comp cal pots.

Taking into account frequency determining components circuit function the following recommended fix refers to modules whose oscillators have errors of 540 hz or more with C1 to mechanical limits. Add 50 pf chip ceramic capacitor in shunt with C1 and 4P7 chip ceramic in shunt with C2. Surface mount capacitors (SMD) can be used easily as there are a number of posts and ground plane areas essentially in the right place for zero lead length. For larger freq errors the limit for C1 shunt cap is 68 pf and C2 is 6P8 before circuit stability may be traded away. Frequency sensitivity of C1 shunt capacitor value is 10 hz per PF and shunt C3 is 17.5 Hz. per PF , C4 has little effect on frequency . Use these values to calculate compensation for other errors.

Module extenders wont be necessary . The test set up to carry out receiver frequency calibration is to apply -80 dbm at 10 MHz to RF port . Set receiver to LSB , 10 MHz plus 1 KHz . Connect LSB line output channel A to Frequency counter. Adjust C1 on synthesiser after15 minute warm up period to gain 10,001,000 on counter. For exciters apply RF output via 20 db attenuator to counter connected to rear RF port. Key in CW mode and adjust C1 for 10 MHz exact.

18th September 2013 , Harris RF 590 , RF-1310 module repair. A9 PLL 4 Assembly. Module repairs continued .Most commonly failed module was the A9 10 Hz frequency step generator which will fail the BITE test and inhibit the receiver operation. The most common fault was the VCO crystal oscillator would not run and electronic checks indicated a faulty crystal aged and out of tolerance. In this case it was a misleading diagnosis . Caution should be exercised in condemning the 20.0275MHz crystal. The following notes relate to the 20MHz oscillator not working as this was the problem in three cards.

The module behaviour was intermittant. and receiver may work for a week or so and then fail. Some mention may be made in troubleshooting strategys to get a fix. It is much easier to work with module extended and connected to its parent radio. Bench operation of loose modules as in this case requires a synthesised HF sig gen, multi voltage + and - 15volt and 8 volt power supply , a 50 KHZ square wave signal source., Spectrum analyser, Frequency counter, DVM and 100MHz CRO.

After carrying out voltage checks on the A9 generally useing DVM looking for simple things, Check all the N channel FETS source resistors voltages as a good guide to their operation in circuit. It is almost impossible to check a FET with the diode test on DVMs. They dont go well in curve tracers either. Initially use CRO and Harris service manual to assess signal operation. To create more AC test points if needed, connect to the leads of the metal film resistors useing small CRO hooks.

If 20 MHz xtal oscillator is not oscillating and intitial checks did not find problem, Remove the xtal and substitute a 20.025 MHZ signal source fed thru two 10 nF caps. The module should work properly and the stage will output signal voltages from T1 that can be observed and if not right attended to. This osc stage has to be right to have the crystal fall into self oscillation. Other supporting stages will spring into operation although J3 output will be slightly incorrect. Monitor A9 RF output on spec- an or freq counter connected to 40MHZ output on J3.

Monitor TP1 VCO control voltage test point and vary the 50 KHz frequency source until phase detector is attempting control of TP1 voltage. That is a healthy sign and resolder xtal back into circuit. Follow Harris technical manual information to complete tests and alignment of A9.

Mechanical faults were found under T1 and L10 with a need to unsolder the xformers and examine closely and repair internal connecting leads . No xtals were found a problem in any A9 module.

21st August 2013: Harris RF590 Receiver, R-2368URR module repair program, Failed modules removed from VK2BLC shack receivers over last 4 years are being processed to restore spares complement. Repair parts are being sourced and aqquired as required.

19th June 2013 : 1KW HF Balun construction, During work to upgrade station 1KW cpability it was discovered the existing balun was saturating or arcing and creating interference to residence digital TV with 1 KW input under some conditions . Was fine with 400 wattsPEP. Work was carried out to build another higher powered transmission line type balun. The antenna was a 40 metre dipole.

Photo shows previously assumed 1KW balun LHS and replacement homebrew 2 to 30 MHz transmission line balun with increased rating.

Design was quite flexible and three toroidal cores similar could be stacked. A larger one piece core was chosen. Enamel wire was replaced by small diameter hardline to obtain increased voltage breakdown when antenna operated at higher VSWR's at band limits . Teflon co-ax could also be used but problems emerged with trying to get the double braided form to hug nicely the ferrite core. The hardline allows this and time will tell if the centre conductor migrates too close to the jacket.. The finished balun is pictured and passed all tests at 1KW at 3:1 VSWR. The frequency response in upper direction is extended and will work to 60 MHz .

Basic tests are loading balun output with nominal 50 ohm resistor . Verifying VSWR VS frequency is better then 1.2:1. This tests for shorts and connectors for finished balun in enclosure .

Another test is to calculate or measure the inductive reactance (XL) betwen the start and finish jacket . The XL has to be more then 150 ohms at lowest frequency. This XL represents the isolation capability of the balun by offering high impedance to unbalance cuurents that would normally flow down the coax feeder cable jacket. These builds of baluns require a non metallic enclosure to prevent stray capacitance and stray induction from changing balun behaviour.

Time domain refletometry ( TDR) was be used to evaluate the cm by cm along the linear length to observe the effect of tight bending of the hardline , each bend can be seen clearly as the effect on impedance can be read out . If any bends are not uniform then a rewind can be signalled where more gentle care can be taken in rewinding the balun. The small diameter hardline in photo adapted quite well to the small radius bend. It was like a concertina in jacket construction.

21 May 2013: Repair and Maintenence shack Test equipment , Repaired HP 500Mhz HP5345 counter mainframe for stuck "lamp test" and insufficient 500MHz clock gate level . A 1GHZ RF probe will be necessary to set up and trace analogue RF levels on the the frequency multitplier and amps PCB. Repair HP counter plug in HP 5354A 4GHz for auto bandselection and deaf for inputs smaller then 270 MHz. Found RF input burned out, necessary to use generic parts to repair . 1205 SMD resistors fine for use in input attenuator as replacements of MELF looking genuines. Use HP SMD schottky single diode SOT packages as replacement for axial germaniums.

15 APRIL 2013: Remote receiver site ongoing work in design and preparing of equipments for site including loom wiring , patch panel configurations , rack power distribution and conversion AC and DC inverters. Source voltage is 24 volt DC and feed 48V upconverters, one 500 VA 48 volt input sine wave inverter is used to power the HF-8050A collins receiver. A quick check of the the VHF link signal levels arriving were 10 plus microvolts and better then 20 DB signal to noise. A site has been chosen for the 43 metre long HF travelling wave dipole and will require 320 metres of buried LDF-450 co-axial hardline cable.

22 March 2013: Remote receiver site ,Construction and design of link infrastructure carried out this month. A new 4 cavity pass reject bandpass filter was homebrewed. -1.3db insertion loss and 79 db rejection at 600KHz for each side of filter was obtained . A order wire telephone was homebrewed, is a 4 wire 600 ohm line level unit with speaker. The shack end patch panel was wired and wiring of shack to ancilliary equipment room was made. Design of link rack system was considered and hardware items sourced. Another order wire telephone was commenced , Learning of the Teknis voice modem and configuration ,looming and facilities in progress. Hf80 equipments will use RS232 at 300 bauds for control. No two way communications on the link channels has been acheived at this time.

February 2013: Commissioning of Station 1 Kilowatt and tests to determine home digital TV RF susceptibility. The sequence was to re-install and rework neihbours TV antennas/cables with emphasis on grounding of mast and good connections and test for adequate TV signal levels . (This was -50dbm). Work then focussed on determining the RF compatibility of the Sony home TV, followed by testing the effect of the RF 1KW power level on home electronics.

The home TV under test was a Sony 40 inch LCD. The Sony can display the Pre and Post-Viterbi bit error rates. Numbers of parts in 10 to the minus 3 is the entry point for the cliff effect or "no signal" displayed, and 10 to the minus 5 are regarded as normal operating area allowing some margin.

To determine susceptibility. Initially a HP8640B signal generator was fed into a 2 port combiner and combined with the digital antenna signal. The 8640 was varied from 5 Mhz to 150MHz and RF level noted to cause pixilisation or "no signal " displayed. It was found the Sony had no RF selectivity to low frequencies and and the threshold level was found to be -10dbm. The implication of this is a high pass filter will be required to cure interference if interference occurs.

The 40 metre dipole was chosen as test antenna and 1KW PEP was applied useing a two-tone source as modulation . The Sony pixilated and some antenna system and supporting hardware issues had to be resolved. The dipole balun core saturated on PEP peaks and required replacement. The DOW key relays in the antenna switch were arcing on peaks and causing out of band spurii.

After resolution of these faults no interference could be observed on the Sony TV .The pre-viterbi error rates were unaffected with TX on or off. Previously with 400watt power levels the TV had been clear.

Photo below : Remote receiver site location for HF receiving antenna array














































Photo above shows: Kombi in use at Matilda Bay Reserve on Swan river, Perth, WA.  Easterly direction is to the left hand side of the photo

























Photo above shows: VW Kombi operators area under construction, homebrew power and radio audio management on LHS and Harris RF-2368 URR and RF-1310 Exciter lower RHS. Aircraft controls interiors are rebuilt to application required . EFDARS control converts to GMT clock and antenna systems controller. Selcall control converts to two tone test oscillator , Data link control converts to audio matrix switcher .

























Photo : Harris system in process of installation into VW Kombi, May 2012. Homebrew frame structure for amplifier RF-1110A

























Photo : Harris RF-1110A amplifier during physical installation, cabling and inverter works in progress. When completed will be demounted and stored as a amplifier system kit to mount in vehicle for weekends away . Antennas to be used will be half rhombic CSA "longshot" broadband horizontal wire antenna and the vertical AT1011 30 foot whip. Estimated install time to re-set up and kit vehicle will be 2 to 3 hours. Power supply wil be modified electrically quietened Honda 2KVA petrol generator


























Photo: VW Kombi 28 Volt homebrew radio power supply switchboard under test























Photo shows VK2BLC ham shack 2013. From left to right CW, VHF 2M duplexer under development , 330 AH 24 volt battery cabinent , essential 24V 100AH battery control and supervision supply dc cabinent, Vaisala weather station control box, vaisala lower cross arm , Collins 180 series SRA-22 antenna coupler, end fed long wire shorting knife switch , AN/TRC-75 air supply blower, pneumatic mast control box and mast lowered. Photo below shows detail of long wire shorting switch.




























Photo below : VK2BLC antennas group 2011. Left to right , 873 KHz receiving loop, top loaded broadband long wire, VHF 2M link antenna to remote site , rotateable 20 M dipole , Centre, 40 M dipole , 80 M delta loop. Block size is 75 by 45 feet.















































Photo: emergency 24V 330AH shack supply. Utilises low cost tool box lined in sections with fibreglass such as floor and lid .

22January 2013: Harris RF-1310 Exciter Memory battery leakage and A14 Repair: This month was spent on repair and maintenence of VW installed Harris system equipments. 

Photo below : Shows corroded and damaged RF1310  A14 PCB when faulty 3.6 volt battery removed from board. 
























Leaking 3.6volt A14 module memory batteries can do considerable damage to the RF-1310 microprocessor control PCB . Most at risk is infrequently used equipments. These premium bathtub encapsulated 150mAH batteries can exude a damaging vapour and liquid silently without operators knowledge and equipments will operate correctly. Eventually a BITE test will fail due to corroded tracks and the damage becomes readily obvious . All RF-1310 memory batteries should be visually inspected for signs of leakage. Two "Datasentry" made in 30th week 1986 have been observed leaking.

The steps to repair the badly corroded A14 PCB are described in following paragraphs.

Wear a anti static strap, ground to radio. . Remove E1 jumper blue link from top of A14 PCB. This disconnects the battery from the electronics. Usecare to desolder battery, apply a lot of solder to pins before useing solder sucker.and desolder the pins so as the battery will come out with dragging out the eyelets.

Use a Dremmel high speed mini general purpose tool and clean off the corrosion untill copper looks like the photo .

Photo shows Harris RF-1310 A14 microprocessor PCB corrosion damage removed waiting for tinning.

When using the Dremmel take care around the inductors. If its needed to do perfect job they can be removed , along with some other components sitting over damaged tracks and refitted later. Even the smallest tracks can be cleaned of corrosion. Use care and tip of metalised rubber dremmel rotating rubber.

Tin with 60/40 solder all over removed corrosion and bare copper. Use heat sparingly to avoid lifting copper and tin all tracks even small ones. Use solder-wick to get desired finish and clear vias. Remove all flux and then apply conformal clear coating.Mask small vias , use masking tape and mask allnearby connectors.

Photo shows tinned copper ready for conformal coating , masking of via holes and connectors still to done.

Fit new 3.6 volt battery unit and if some PCB tracks look possibly open do the ohmmeter check using the overlays and circuits in manual. Use edge connectors as part of measurement circuit and to destination. Areas most likely affected wii be U6 4021 IC and J6 connector.

Check new battery has at least 3.6 volts open circuit and charge if necessary. A flat battery at 0 volts can damage U16 ROM if 1310 powered up.

Move link from strorage position E3 to operate position E1

Photo shows completed repair.

22nd December 2012: Minimum RF Powers for CQ Daytime HF Mobile operations in Remote Areas: Some thought and some experimentation was given to mobile antenna installation and type and transmitter powers. The analysis model was based on how many unsuccessful/successful times a CQ call was made on both 40 and 20 metres over amonth period originating from Perth.Two completly autonomous HF systems were set up on the VW and could switched between antennas at will and powers controlled.

One installation was a standard 8 foot whip and base fed in line commercial tuner and the other a 16 foot bent over the vehicle base fed whip antenna with a military spec antenna coupler . Communication distances included local to 30 kms.Taking 100 watts PEP as minimum calls would be made first on the8 foot vertical in group of three of 20 seconds over 2 minutes then switch over and repeat process on the 16 foot system. The significant result was that the bent over configuration consistently outperformed the 8 foot system in initiating a cold contact. If too much power was used initially then signal reciprocal problems emerged. There was a need to seek a balance.

Given the mobile noise levels, stations returning calls could fall below the workable average mobile receive levels . It was more desireable to gain a contact on 100 watts , then increase power after the contact was made. The VW vehiclegenerated noise has been supressed to 2 microvolts, however signal fading and external network power line hash require at least 10uV received signal if mobile . This is the case when useing the system on work commute from metropolitan areas. Suprisingly in the country rural areas many of the power lines are noisy.

20th November 2012 : Harris Installation VW ongoing work on support infrastructure. Load testing of the 28 volt system driving 1500VA sine inverter shows a 1.7 volt drop across the lead acid battery when step loaded with 90 amps continous. With 1750 peak VA of load and 1150watts actual real power for 400 watts of RF output from RF-1110A amplifier. AC system regulation is within 5 volts of 240 volt nominal. Power levels of this dimension are not handled well by compact batterys in mobile applications . The mobile AC system lends itself well to running mains operated receivers. These test results suggest transmitters are best utilised if directly operated off DC source. Wiring looms, breakout box and harness installation of monitoring instrumentation wiring was completed.

18 October 2012 : Homebrew 600Khz split 2 Meter Duplexer: To mainly save on costs of 120 metres of LDF450 heliax cable it was decided to use a duplexer to eliminate a large list of RF antenna hardware and halve the number of antennas required. The 600KHz narrow spacing requires some attention to the design 2 Metre TX power was 25 watts and receiver was 0.5 uV sensitivity.
























Photo:Shows completed homebrew duplexer under test. HP 8505A Vector Network Analyser is used to sweep complete duplexer and check final performance specifications.























Photo: Completed Rx/Tx four cavity pass reject duplexer , each cavity was built up from pre-existing lower frequency cavities, outer case was left unmodified and internal tuneing posts shortened Coupling loops were modified.

Photo: VNA display of testing fromantenna port input and to transmitter input port. Top trace is looking into the antenna port and shows input return loss notches of both cavity pairs. Channel spacing is 600KHz, RX and TX paths.Receivepath input is terminated in 50.0 ohms. Displayed is 28.6db S[1.1] showing a good match to transmitter, scale is 10 db per graticle line. Lower trace compressed by 20 db a division shows the rejection value for the receive path of -73.9 dbc. S[2.1] at receive frequency.When final tuneing is done with the actual TX and RX and antenna connected, negative 79 dbc is acheived. For a 0.5uV sensitivy RX with 1uV set mute threshold no RX desensitisation by transmitter broadband noise is observed.Note the unequal values of the dips in the top trace--this is a guide the build correctness of the cavity pairs combining harness. Aim is to make these dips equal. If not then no other dip should be less then 20 db.


Two design options exist , use a coaxial ring Hybrid with one cavity fabricated with semi rigid coax or put together a 4 cavity band pass , band reject design with quarter wavelength coupling cables to connect together. The band pass band reject design was chosen.























Photo: Shows standard pass cavity loop modified to incorporate series capacitors to convert to band pass , band reject type cavity . One cap is adjustable from outside cavity . Others increase capacitance to gain desired tuneing range .

Four seven inch diameter 2 port cavities are required to be modified to one port with T piece, band pass , band reject types, Two are used in RX path and twoin TX path. Modification involved calls for one coupling loop to be modified to have a Johannsen ceramic or glass trimmer used to series resonate the coupling loop. The trimmer is installed to allow tuning from outside cavity and is located almost on the N connector . This will produce the notch





























Photo: The Homebrew Duplexer Installed temporarily waiting for shelter cabinent

To modify lower frquency cavities not useable directly on 144 MHz it is only neccessary to dismantle and cut down the length of the internal tuning post .No change is required to outer case.

Two cavities used in the TX path joined by quarter wave links cut to take into account the internal coupling loop lengths and cable velocity factor. Cavities are adjusted for TX freq pass and Receiver notch . The cavities one port with T piece connector links in and out on same port. Likewise two cavities used in RX path , tuned to pass RX and notch TX freq. The two groups are joined by a combiner harness of of two quarter wave lengths and a T piece. See google references for fine detail. 38 db notches should be easy to get. with each 7 inch diameter cavities

Use a synthesised signal generator to obtain frequency precision required. Use a swept return loss system of some sort to observe behaviour of modified cavities an aid in cutting of quarter wave link cables and harness.

Performance of the homebrewed duplexer had insertion loss of around 1.5 db and rejection of 104db on each path. That was sufficient to be free of RX desensitisation.

29 September 2012: Remote HF Receiver Site : Work is in progress to conduct path testing .Two 2 metre log periodic 7 element yaggis were fabricated and optimised individualy, then as a bore site pair , optimised some more by operating facing together over short distance and sweeping like a filter. Element lengths were adjusted in 5mm increments. Some 10 mm changes were made to calculated lengths. Heliax was installed and antenna mounted one end of link. A link transceiver was configured from surplus equipments. Useing google earth and some knife edge refraction modelling applied to the three consequetive ridge lines in the 12km path to estimate signal strength at remote site expected. Useing Wouxin hand held 2 metre tx/rx the path was traversed with 10watts applied to the test antenna . 0.5uV is received at 8 feet above the ground . Thats a path loss of 150 dbm uncorrected. Knife edge calculated was 86 db . The additional loss may be accounted for in the fact the handheld was too close in the lee side of the third ridge. The RX site yaggi is yet tobe installed at 70 feet height. Work is progressing on the design of the telemetry, multiplexed with voice configurations and hardware.

28th August 2012 : Harris VW Kombi Install : Work continued on design and fabrication of the intermeidiate control , power supervision looms and breakout boxes to install the systems control console. Problems are being experienced from the transient start up current of the Harris RF-1124 switch mode supply . When the van is on the end of a standard mains extension lead the amplifier cannot be started.Support equipments shut down, It is possible it is a 4500 VA transient . It is theinstantaneous charging of 4000 uF capacitor to 380volt DC. A soft start mains interface design will required to to lengthen the start up cycle. The amp will be set for 400 watts on standard 10 amp circuits.

1st July 2012 : High power switchmode AC inverter RF noise Suppression: Work on the VW Kombi as a radio communications platform continued, It was found necessary to investigate and suppress the RF noise from the solid state 1500VA 230Volt AC inverter .

This inverter operates the Harris R-2368URR receiver and the RF-1310 exciter from the 28 volt DC supply. Operating current if fully loaded is around 70 amps and the protection is chosen as 100Amps. The sine wave inverter is a semi commercial mass produced unit manufactured by Powertech . The unit contains very little EMI measures.

Before adding filters the 2368 RX indicated around 30 uV of noise response at 14 MHz when receiving the whip signalsaround a 8 on the S scale. Bringing up a HP141T Spec and current probe on the DC rail near the inverter input , the noisepeaks was observed as -40dbc or 2.2mV. Suppression was indicated to reduce this to >-100dbc where 0dbc is a 22.4 millivolt across 50 ohms . External filters will be required as there is little space inside the inverter to incorporate. A few guidlines can be suggested.

Since the inverter input circuits float it is necessary to RF strap the negative rail to inverter chassis A copper sheet of generous width is used to bond the negative terminal to invertercase and continues in distance of a inch or so to form the base on whicha 100 amp pi filter block was installed . This guarantees the filter will be effective on the only conductor has noise on it otherwise the negative line wil radiate RF noise. 47 db attenuation was acheived at 14 MHz. on the DC supply line . The bonding should be at the connector terminal itself direct to case.

A 230V mains double pole 10A filter block will be required for the inverter line output , Even if this is a small distance from the inverter a braided screen is necessary over the length grounded at both ends. Use braid salvaged from a piece of RF214 coaxial cable and thread over the line wires. The metal case of the mainsfilter needs to contact the vehicle metalwork securely.

The filtered side can run wherever. The end result was the R-2368URR receiving system noise injected level fell towards 1-3uV.

The fitting of filtersreduced the radio systempicked up inverter noise to around S2. S8 to S2 is 36DB change.

The magnetic feild RF interference from the sheet aluminium clad inverter extends to around 2 feet and diminshes rapidly with distance . The inverter should be mounted away from the radio equipment .


5th June 2012 : HARRIS RF-1110A Trouble Shooting: Work continued to bring to full functionality a RF-1110A linear amplifier . Performance testing showed the amplifier could not acheive more then 200watts RF output . The driver module was faulty and replaced . Further testing showed high intermodulation distortion at -20 dbm. 1KW PEP RF output . Two Power amplifier modules output was below spec and the amp could not reach 1300 watts for setting up the transmitter final amplifiers protection TGC .

It was found one power transistor of the four in each module had failed. Some observations can be made about this bulk failure. The design of the Harris amp by useing PA module based combiners with power diverting dump resistorsact to protect the devices from excess RF voltage mode failure. The waster circuitry in the chassis mounted 4 way combiner module further aids the excess voltage mode protection ofthe devices. The RF output devices were damaged by current mode failure. The weakest of the matched pairs failed at overload conditions. Voltage mode failures leads to shorted RF output devices and current mode failure leads to open circuit devices.

If these surplus amplifiers are intended for use as amateur linears consideration has to be given that when the driver module is removed and this node is used to feed normal ham transmitters to the RF-1110A with around 80 watts the linear has no protection against excess drive. All protection systems have been defeated since the gain control devices are either in the RF-1310 exciter or in the Driver module itself.

The only protection still available is the current limits of the RF-1124 power supply. Since that is 80 to 90 amps at 50 volts this is near 4,500 watts input and will result in RF outputs near 2KW PEP. The amplifier is suceptible to failure at these power levels.

The RF-1124 current limits should be reset to limit DC input 2,400 watts if no design way can thought of to enable a ALC power control loop around the amplifier including its driving source.

























Photo: Harris RF-1110A amplifier (top) and RF-1124 power supply installation in VW Kombi. Weight and balance determined mounting location.

14th May 2012 : Harris RF-1124 , Power Supply Trouble shooting: Tasks this month was repairing the 3KVA switchmode 50Volt DC 80 ampere power supply that powers the Harris RF-1110A 1 KW HF Linear amplifier. Some observations and hints to service to this SMPS ( switch mode power supply) can be made. The main fault addressed was B supply of the two 40 A modules was ina condition that loads over 1.5 amps would trip the module. This repair supplements a sequence of operations to commission a RF-1130-02 system.

Usefull features are even though unit is 3 phase at 115 volts itcan wired at the power connector to operate single phase on 230 volts. The sucess of the power connection can be monitored on the 250 V module A2 by viewing the LEDS. The correct two phases indicated of the three possible must be lit for the power supply to work. Voltage changeover is by a pointer switch on the A4 module. Australian users will need to use a isolation transformer to prevent the SMPS input EMI filter from tripping the earth leakage breakers. Also using the isolation xformer givesa degree safety in servicing the main 250 volt switching circuits if required.

The repair of the neon bulbs on the front panel can be accomplished by soldering in small easy to source neon bulb elementss after breaking out the old glass. The 250 volt DC neon is important as a visual guide to the health and status of the 350 DC across the main electros.( For safety reasons). Control boards will require module extender if efficient trouble shooting is to be made.

The real success of this power supply lies in the long wiring loom tails on the main switching modules A5 and A8 ,allows them to mount on say tempory plywood sheet for service access. The module itself has swing out sections . Using a 2KW dynamic load and DMM it was possible to trouble shoot the control circuits with ease.

Servicing was acheived with RF-1124 connected to its associated system components.

24th April 2012: Harris RF-1110A Amplifier system: Time was taken this month to familirise and understand the build, test methods and performance measurements fo the amplifier and its associated power supply.


22nd March 2012 : Harris RF-1310 Exciter Troubleshooting Methodology: Work continued to determine the prefferred way of approaching an unknown radio from long storage or unknown source. A recommended sequence 1) check radio mains voltage tap, 2) check internal hi stab oven power supply tap, 3) check RAM storage jumper on A14 and RAM battery voltage 4) charge if zero volts, 4 ) place jumper in correct operateposition. 5)Remove top cover of power supply ,make DVM available atBITE test point group LHS when viewed from front.All radio voltages can be measured here , 6) Apply mains power to radio watch for flourescent displays to lite and boot sequence to take place.If display remains off, turn off. Check manual for map of voltages at BITE test points., prepare to measure quickly all voltages after switch on. One supply rail may be found near zero volts. This indicates a shorted tantalum capacitor.























Photo: Shows underneath view of Harris RF-1310 Exciter

The method here is with mains lead disconnected is use DVM in ohms position and test the Bite test points to ground. The faulty one with will be in the range of 0.8 ohms. Leave the DVM connected. Remove bottom cover. With reference to tech manual see that a particular set of module power supply interconnects use the white coloured plugs. Not allwhite plugs are power plugs. Check!, Watch DVM as each white plug is lifted and it will be noticed the meter may jump to high impedance readings, follow the trail so to speak to systematically arrive at the actual faulty PCB . There are some power plugs that are in combination with other circuits and are actually Berg black plugs. This particularly around the front panel. It should be within half hour to get to the exact location. Not all tantulums will burn and smoke if power left on so this method is not recommended . Once the shorted PCB is identified. Check circuit and choose tants that are sitting directly on the power rails. Use DVM to check each one individually matching probe polaritys with the polarity of thetant under test. For replacement recommend removal and fitting from the top. Wear static strap when ever working on the cards of a RF-1310.

Once power rails have been established on power up "RAM memory failure " may flash up on display . Ignore that and start programming frequency and mode if the radio will allow a frequency entry all is OK. Give a bout 4 minutes and run the BITE test . If any BITE fails use manual to take further.

20th February 2012 : Harris RF-1310 Exciter Repairs: Tantalum capacitor failures have been found to be a problem to those experienced in HF-80 equipments. For harris exciters stored for long periods or have infrequent use a failure of tantalum capacitor anywhere within the exciter is quite certain. A number of search methodoligies were trialed . One siginificant discovery was made . It is important to test any spare part tantalum capacitor before insertion. A high rate of failures were found on new sparecapacitorsheld for repairs. The failure mechanism applys equally to new tantalums held in stock.

26th January 2012 : Harris RF1310 memory failure problem. If exciters are left stored withoutdisconnection of memory batterylink.( follow instructions in Harris manual for this operation) Then if nickel cad battery goes to zero volts. When switched on for the first time the LH5116-10 RAM will be destroyed. After long term storage always measure memory battery volts. If completly flat charge enough for it to be operational. If rubbish appears on RF1310 and unit fails to boot and fault on suspect the RAM chip . Recommend to fit IC socket when replacing this chip .























Photo: RF-1310 Harris exciter shows IC socket in position (4th chip from LHS bottom board ) shows location of the LH5116-10 RAM

Storage periods over a year can produce this failure mode. Use anti staticstraps when working on this PCB.


29 December 2011 Collins 490T-1 antenna couplers : It has proved difficult to use 490T series tuners with non Collins equipments. A working bee was made to better understand the tuner characteristics and specifications and in the process repair several couplers. The 490T-1 tuner is a full self contained unit requiring 120 va of 115 volt 400 HZ power to operate.

The majority of failures lie in the seizing of varicoils or faults in the complex tuner control module. It was necessary to use the Collins 878L-15 module test set to locate the faults inthe coupler module. The module controls a high speed mechanical system nominally taking 3 secs to complete and making understanding any faulty tune sequence too difficult. The test set applys steady state conditions to exercise the relays and simulate functions. Readout is by lamp pairs where a illumination of a pair denotes a succesful test. 

Photo below shows :490T Coupler Control Module inserted in the 878L-15 module test set.

















The main difficulty is the 490T requires greater then 65 watts present during the tune. Most solid state 100 watt rigs RF power output dies rapidly when SWR exceeds 2:1. For the initial activation of the tuner 16 watts is commonly seen, far below the requirement. Tube PA amps can hold up the power under SWR conditions better. A minimum 200w watt solid state amp is required and a series 50 ohm resistor switched in and out after the tune complete. This locks the maximum SWR to 2:1.

To do the work a complete Collins 618T test bench was set up in conjunction with 678P-1/2 radio set test harness. It was necessary to service the 618T to obtain a uniform 100 watts test power on an yHF frequency. The 618T used was 618T-3B 28Volt DC powered unit. It will be necessary to make adjustments to any 618T that has been in storage for long time. The most dominant determinator for obtaining uniform power VS frequency will be the TGC pot found on the power amplifier module.

The 490T was easy to repair to module level and capable of high performance . Tuning was observed to be just a blurr of high speed mechanics and final tune SWR's were very low and consistents near 1.25 to 1. Besides the tune power and 400Hz powering problems a series inductor will be required to tune a 12 foot whips at very low bands . Use the Collins 690D-1 load coil and antenna base and AT1011 fibreglass antenna whip sections. This assembly was part of the AN/MRC-95.

23 November 2011 HF-80 : Work continues on maintainence and repair of HF-80 components, It is still obvious only the faulty tantalum capacitors need replacement in repairing HF-80 receivers and exciters. Subsequent burn -in periods and switch on cycles have not yielded any further failures.

18 Oct 2011: Remote receiver project . Due to excessive electrical noise which now originates from the newly installed neihbourhood solar power systems when feeding the grid (broadband frying pan sounds) , noisy switchmode computer power supplies ( narrower broadband bandwidth and drifting freq, some carriers buzzing, duck sounds and other personalities) , digital TV's and energy saving light bulbs now produce a constant interference noise floor with little hope of resolution. Has made seeking a remote receiver site imperative. Work is proceeding to assemble all the needed equipments. HF-8050A/HF-8091 was chosen for the HF and Rhode and Swartz VHF transceivers for the 2 metre link application. Diplexers are used to simplify antenna requirements, LD-450 heliax and components , AC float DC power supplies , inverters and control and supervisory panels are in progress. The HF remote antenna chosen for the application will be AEA (Antenna Engineering Australia ) broadband travelling wave antenna for larger remote site or a Rohde and Swartz Active vertical antenna if small site.


27 Sept 2011: Collins Rockwell HF-80 receiver repairs workshop: While waiting for the weather to improve for outdoor ham projects a number of HF-80 receivers were repaired, all had shorted DC rails on switch-on due to degraded tantalum electrolytic capacitors prematurely breaking down. In some case the shorting of capacitors takes place up to 3 minutes after switch on. A service methodoligy was devised to restrict further damage to series chokes. A number of steps area recommended.

1) Immeidiately fix the S-Meter panel lamps. The relative brightness on these can give some visual clues as to how much load is on the powers supplys.(use ohmeter to check bulbs)

2) Remove synthesiser cover and remove all cards , Remove all other plug in cards cards elswhere in the receiver. Wear static strap when handling modules grounded to case. Handle cards only by edges. Set down on static free surface.

3) Switch on RX , Note normal brightness of S-meter lamps and measure power supply voltages at terminal board on power supply , should be OK. If there is short, it will be under the synthesiser cage . Access that area and test those tant caps with ohmeter.

4) Replace the cards in following order switching on and off the RX each time . Replace Digital cards first , Observe each time power supply rails remain normal, followed by loading up the synthesiser cage. Start with regulator card , It has voltage test points which can be checked. Turn on RX and check and turn off for each inserted card, then insert Divider boards one at a time. The small chokes will burn up more and smell will be obvious. Insert the last more complex module , the PLL mixer /LO system card. This one is more likely to have a shorted cap.

5) Insert the audio and AFC boards next. Then the translator metal box. Caps have been seen shorted on the translator (check with ohmeter as they are easily accessible ) .

6) Insert the IF boards one at a time and wait and observe closely for voltages to remain at normal . Turn off and insert next one . In most cases always there will be IF board shorts.

7) Since the failed tantalums always short circuit and a number of modules can be affected, this sequencing method allows checking and observation of each card individually and power supply voltages can be measured at that moment at the power supply terminal strip at the rear of the RX if needed. Reduced brightness levels of S-meter can indicate there are problems as rough diagnostic aid.


15 August 2011:Collins Rockwell HF-80 tantalum failure mechanisms: Some investigation was made to explain why Tantalum capacitors fail in HF 80 series equipments. A number of pertinent points emerged, Receivers stored for 4 to 8 years or longer without use are certain to suffer cap failure on switch -on. Only the tantalum caps directly connected to the main DC power supply rails are at risk of destruction. Despite the caps reliability they are not rugged when current surges exceed the storage degraded cap ratings. (reduced safe operating voltage)

Bead tantalum caps used in HF-80 series equipments are specifically designed to their operating voltages. They are capable of long life in regular use. The chemical mechanism on which they depend sets this operating voltage. This voltage can degrade to a lower voltage in long storage . The surge capability is correspondingly lowered . Essentially excessive capacitor surge current follows from the lowered new operating voltage. The capacitor then looks like a low resistance at what was the normal radio rail voltage. The capacitor current curve if plotted with increasing voltage looks like one associated with a zener diode if there was no current limiting resistor . The physical micro structure is not capable of dissipating the localised heating energy and basically welds the two formerly insulated surfacesof the capacitor structure together. Producing a low impedance short circuit.

One fix since the power supplies are linear, it is possible to run the Receiver newly removed from long storage on half mains voltage for 15 minutes or longer to soften the switch on surge and attempt recovery of the aged caps.. ........ .

There is no need to replace any other capacitors in the HF-80 other then the faulty ones.

Capacitor manufacturers recommmend either of two solutions. a) Use caps with a much higher operating voltage. EG use 50 volt types. b) Insert a 1 ohm to 3 ohm series resistor in series with the dc rail directly connected caps.Some caps are partially protected when sitting on load side of RFC rail chokes. Obviously this is not so practical , best fix is to use the Receiver at least every 3 months.

13 July 2011: Short range microwave link. With inclement winter weather curtailing fabrication work on the VW Kombi ham station an examination of ham salvage microwave assets was made and work commenced on fabrication of short link with TX powers of 100mW at 10 and 5.8 Ghz to enable remote control of VW ssb radios from less then 500metres (750ft) . Required was duplex voice channel and duplex RS232 2400bps data , one order wire and one supervisory telemetry . Using Ericcson and NEC earthstation surplus bits a RF system so very similiar to the ericcson minilink solutions was fabricated and successfull. Simplification of the re-design of the baseband and multiplex electronics is in progress.

12 June 2011: VW Engine instrument cluster. Due to high current draw of VW radio system , engine is needed to run continously , additional monitoring is needed since a VW engine is aircooled. A cluster was homebrewed based on modified aircraft instruments/assemblys together with wiring harnessses , remote breakout boxes and sensors. Where required, internals of gauges were rebuilt to make DC operated rather then 400HZ 26 volt ac . Some new circuits were developed . The original scales and functions were preserved . Calibration to match scales markings and tracking were performed with test sets DrucK for pressure , Fluke for thermocouples and Load meter shunts.


These notes apply to the flood of 2 inch round instruments sourced from several low cost vendors in USA having many cockpit functions, some are 400Hz operated and more challenging to modify as mentioned below. Best meters to experiment with are the DC and AC loadmeters made by Weston and have dc moving coil movements. The scales can easily represent DC voltages to 15 volts and DC amperes to 15 A by scaling. The AC loadmeter has the most internal space to add custom circuitry

Most of the surplus aircraft 2 inch oil pressure instruments are of the electrodynamic type that use two coils , one fixed for the circular soft iron magnetic path and the other is the moving coil. These can be wired to operate on DC however non linerarity affecting the first 20 degrees of pointer will be noticed and the main problem is hystersis if calibration is performed for pointer moving clockwise and different readings will be obtained when pointer moving anti clocwise. The final problem is remenant magnetism preventing the pointer resetting to zero. Most of the L1101 and airbus and boeing instruments are of this type. For these reasons are more difficult to put to use since they were based on 400HZ operation.

The most usefull lowest cost 2 inch intruments are the Weston load meters scaled 0 to 1.5 , they have space inside for additional circuitry ( AC loadmeters have more), ease of dismantling, dc movements, ease of changing instrument markings like volts etc, adding scaling text .Applications i have been pursueing are RF power meter 0 to 1.5KW, VSWR meter0 to 1.5 SWR and 0 to 15 VSWR, DC voltmeter 0 to 15 V and DC amps 0 to 15A.

Most of these instruments require 5 volt lamp supply at around 0.4amp. Can be AC.























Photo: Homebrew VW engine instrumentation cluster and breakout box .

20 May 2011: VW Kombi operating desk, Work continues on design of small control console to take audio ,antenna switching functions and performance monitoring control boxeslocated close to operating area. A multipurpose irregular shaped rack using aircraft instrument standard dimensioning is required. New cable way ducting underfloor using shaped fibreglass brackets , covers has been installed.

18 April 2011: Linear amplifiers/ VW ham station. A intermediate 100 watt linear amplifier application for use between the Harris RF1310 and Transworld TW-1000 amplifier was consideredand a Barrett SB225 transceiver Power amp module was tested. Was identified as a solution with 40 db maximum gain open loop and integrated ALC loop around module stand alone. Most military exciters output 100mW maximum and most amateur amplifiers require 80 watts drive. The system overall ALC can completly cross over the intermeidiate stage and control the output linear stages. The adapted SSB commercial amp modules can be imbedded and form a solution to this incompatibility problem.

Further work was carried out on the VW station and related to the support infrastructure, more interconnect wiring and instrumentation was added and a aircraft packaging standard has been adapted using standard aircraft control head widths and Deuz fasteners for rapid upgrades.























Photo above: Hombrew screened ignition harness for VW Kombi
























Photo above: Shows homebrew ignition harness fitted to VW Kombi

12 March 2011. Sheilded Ignition Harness. A screened ignition system was fabricated for the VW Kombi from baked bean and fruit tins along with some aircraft salvage items and fitted. The spark plug noise has become inaudible on all bands with base loaded whip antenna within 2.0 metres of engine.























Photo above shows : 873 Khz loop antenna , 4 turns, spaced to reduce stray C , 470pf resonating cap, capacitive divider matching of loop to isolating balancing transformer. Antenna was designed to replace the 25 metre long wire and make possible continued reception of 2GB in Sydney in the prescence of the increased background noise level.

17 February 2011: Loop Experiments , The steady state now QRM levels at Dubbo shack have made ham operations almost a no go with excess of 20uV average level 24/7 on 14MHz . 50uV on 7 MHz. The nature is just a soup of broadband noise similiar to power line insulator noise but many sources. After recent heavy rains made no difference to the QRM so not power line . Will need a remote HF receiver site to fix this problem. Did build some 1.7 metre receiving loops and when balanced can reduce noise by up to 20db but too early yet to have full data. Found larger delta loops asorbed power from colocated dipolesand require vacum relays to open them when not in use. Could only get 10 db noise reduction.

Photo below shows: The broadband EMI present on the 40 metre dipole as seen by a HP 141T spectrum analyser centred on 7MHz , Reference level 0DBC is equal to -20DBM. Scale horizontal is 1 MHz per division, Vertical scale is 10 db per divsion . It can be seen the noise level is -58DBC. Trace is one shot and taken around 2pm. The dominant interference is from 4 nearby solar systems- this becomes obvious as the peaks of the spurr are first viewed to moving in frequency when viewed . Switching the analyser to line triggering ,all the spurrs then lock in and display becomes static and only change up and down in amplitude. This indicates the the EMI is sourcing from mains switching devices , A good healthy radio noise environment for SSB receiving would be around 3 uV or approximately -100DBC.























17th December 2010: HF Linear amplifier design, working on 1st and second amp low level stages, comparing use of motorola fat film hybrid with discrete transistors. Design requirement is for 20 db power gain. +20 dbm input. Also this month the building of a replacement Neihoff voltage regulator for the Kombi van

Design and fabrication of replacement regulator for Niehoff 28 v 30A brushless alternator.

A homebrew miniproject was carried out build a regulator out of the salvage of the faulty one. Fundementally the cicuit is a high current temperature compensated comparator. It was designed by extracting ideas to form a practical circut. It was fabricated as shown in vero version below and tested on the bench before installation in the recovered metalwork. The alternator feild current is around 3 amps and will fall to zero when alternator voltage exceeds 27.6V. Some work is needed on timeconstants in DC control loop to prevent instability. Additional accesory circuit added to power Alternator Lamp and the current through this bulb initially excites the alternator feild to enable operation. There is not enough iron to have sufficient remnance feild to make alternator self exciting. A heat gun is used in diffuse way to test temp regulation stability.

Photo below shows : An unsuccessful attempt to get access to the circuit board to make a repair. The encapsulated nature of the regulator eliminates repaireability. It was decided to use all the existing metalwork after cleaning it up.











































Photo above shows: Homebrew Neihoff alternator regulator prototype based on design ideas from VK2ABN

The OK Corral method has been devised for the vero board application to avoid installing components on mirror reversed side. The PCB is circled by ground tracks to build a circuit cage. Then the components are mounted exactly the same as seen in the schematic drawing (coralled inside) . If Vero used for a RF build then the ring of solder blobs are linked , a stick-on copper film sheet is applied to otherside and RF stitching pins are used liberally to join sections and traces transverse to create ground planes and useable microstrip. To acheive the circuit to vero board translation, schematic is redrawn a number of times to be exactly the same as the proposed layout. Various rules can be applied. VCC from top strip , inputs to LHS, outputs to RHS , grounds and returns to lower strip. The interface connector to alternator is under the matrix board or its top side.

30th October 2010: HF Linear amplifier design, considering packaging and mechanical integration solutions for the main mechanical sub assemblies. Number of mini designs for assemblies such as control and supervision card frame, interwiring terminus, air coolant plenums , low pass filter enclosure to be firmed up. Buying of components continueing.

06th September 2010: HF Linear amplifier design in progress. One area advanced for early assessment is the switchmode power supplys RF switching noise levels that may be received by the co-located communications receiver. It is necessary to do some pre design lab work to examine the magnitudes of the rf noise escaping from the selected 1200 watt 48volt power supply module in the proposed compact metalwork to determine filtering and sheilding partitioning required. The aim is to intergrate both RF amp and power sources in one cabinent.

09th July 2010: Perth, Harris radio systems VW Kombi fitout (cont) in progress, Working on using modules and PCB's related to the RF-1110A, need to integrate into a 200 to 400 watt 40db gain power amplifier design with ALC in 6RU format based on the engineering personalitiesof Harris. Some previous breadboard attempts were a failure with extensive home brew content. This attempt will basically be a reverse engineeering one. However module integration and hardware and cooling issues will be a fresh approach.

08th June 2010: Dubbo, Continued work on solutions for excessive local 24/7 electrical interference radiated from power line, basically an electronic soup wideband pink noise (50uVaverage at 7MHz in 3KHz BW) with a additional peak at 14MHz (20uV average )and attenuating in level after that. Superimposed on the noise floor are a myriad of individual unstable frequency spurs spaced in 100KHz groups to 1mV max level across ham band. (off dipole and vertical antennas) . Since November 2009 there has been a step increasefrom 5uV or +20 db in shack noise floor. Ham operations now exceedingly difficult. Completed rigging for 80metre loop and working on impedance matching. Have been looking for country location for remote HF receiver with 2 mtre link path.

24th May 2010. Dubbo, Found HF operations very difficult. In order to maintain amateur operations it will be necessary to find solutions.HF radio 80 metre noise floors now at -55 dbm wideband in my suburban neihbourhood. Work well advanced designing and fabricating one small 2metre and one halfwave 80 metre loop to investigate noise reduction capability for receiving applications supplemented by standard antennas for transmitting. The noise floor of exact location was -105dbm in 1964.























Photo above : Experimental matching network in development, LHS loop antenna (not visable ) is connected via series inductances to a balanced PI network to generate a 600 ohm antenna input , The matching wideband RF transformerconverts the antenna impedance 600 ohm to 50 ohm ( RF xformer RHS).THe L and C networksdetermine the 80 metre small loop resonating and matching network component values. The one drawback of the small loop is the high Q and narrow bandwidth. Photo below is the test instruments used in developing impedance matching circuit , HP4815A impedance meter and monitoring counter for accuracy .























1310A installed in Kombi. New 24volt, multi voltage instrument power supply for control boxes and 5 volt aviation intrument power , 400Hz for servo systems refurbished and 240v 1500va inverter installed . New master and ancillery control panelsutilizing surplus L-1101 , DC10 and airbus instruments and control boxes components installed. Power amplifier configuration under consideration.

10th MAY 2010. BARRETT 910 HF TUNER UPGRADE: Barrett Communications 910 Antenna tuner was modified to make it more usefull in amatuer radio service and generically compatible with any radio set .






















Photo:CSF Thompson AN/TRC-300 with modified Barrett 910 auto antenna tuner

Converted civilian tuner type to incorporatemilitary features. Fitted bendix connectors, Removed all flying leads, rewired internal RF path with RF 3mm strapconductors, incorporated EMC mods by adding filters on all DC and control leads. Incorporated a large internal shaped ground buss plate to receive the RF connector , added a bottom drain hole for removing internal condensation and repainted case. Designed a small remote universal control interface. Tune initiate in this coupler control methodoligy is to momentarily interrupt the 12 Volt supply line.


04 April 2010. Harris Receiver R-2368URR speaker installation: Receiver control problems were experienced with Visaton FR8 loudspeaker fitted. S24 RF manual gain button would stick closed locking out the keyboard. Problem was traced to the stray magnetic field from the speaker parasitically operating the switch mechanism of S24. A number of fixes to sheild the field to the switch are possible. The fix chosen was to fit the body of S24 with a stainless steel hose clip 8-22mm. The most obvious is to choose a speaker component without as much magnetic flux leakage.


31 March 2010. Harris coupler CU-2397/G coupler system integration, Designed a system interfacebox between TW-100 and 2397. Requires two pulses with delay to control 2397 from single ATU button on TW100.






















Photo: Shows homebrew Harris CU-2397/G fast coupler generic interface

Acheived with monostables. First home reset pulse must home coupler followedby Keyline activation within 0.5 second together with application of RF tune power. Implemented in small diecast box with manual control option and Bendix connectors. Lamps: Fault, Power , Tune in Progress.

Solve fail to tune problems of 2397.Determine TX tune power must beset to at least 40Wdue high SWR's . If tune power falls below 10 watts for any reason during tune the 2397 will abort the cycle. Very wild reactive impedances are present at tune onset. Solid state HF amps fold down over 2:1 VSWR.

CU-2397 performs well and final SWR does ripple with 1.6:1 being typical. Lower SWR's exist for certain matches. 3 secs and less is typical tune time for new frequencies. For frequencies previously used tune time is less then 50 mS.

Actual tuner efficiency and losses will be evaluated at later time.


25th February2010. Harris 2368URR speaker addition. The Visaton 3.3inch FR8 8ohm voice coil ( see RS catalogue) is a suitable choice to fit the Harris front panel. It may be necessary to slot the two right hand side holes. (speaker veiwed from front with terminals down) to aid fitting. It will be necessary to loosen the meter screws . The switch bracket PCB mounts on top of the speaker frame when in position. The speaker wires will be found in a bundle of heat shrink at the receiver rear near the position where A23 is located in diecast housing. Care needs to be taken with speaker magnet fouling loom wires and nearby circuit boards. Use antistatic measures when working in speaker area.






















31st�January 2010. R-2368/URR speaker addition. The R-2368 receiver is not fitted with loudspeaker but has most of wiring looms and provisions to add a loudspeaker. The problem is the speaker requires carefull selection due to its small size . Spent some time searching for a suitable unit with 60mm by 60mm mounting holes with wide range response. Such a suitable replacement is the Visaton series of 8cm/3.3 inch units such as the FR8. Currently i am building a vero board based amp using bridge connected LM380 IC's.

Photo below shows dominantly receivers this side, Photo RHS shows dominantly exciters this side





















Photo below shows  : Station ISB 70 volt loudspeakers Technis amplifiers , station desk patch panel, two tone test oscillator.























20 November/December 2009. Harris remote and audio system integration and instant proof of performance test facilities. Completed RF1310 remote looms to 3 metre distant RF-110A. Completed 19inch rack based bidirectional 600 ohm audio interface system equipments and loomings using ex RAAF Teknis amp module series, Ring tip sleeve patch fields, Mike and 10 watt 600 ohm speaker amps modularised in ISEP frames, and installed with ex Navy 2368-urr receiver matching 70volt ships dual loudspeakers for ISB.Single desk mike becomes audio source for all transmitters. All Transmitter and reciver systems patchable at one location. Completed install of test instrument suite ,19 inch 2-tone oscillator,AWA auto N&D set, HP141 Spectrumanalyser via Bird sniffer,Tektronix PEP envelope CRO and W&G PSM19 AF Oscillator allowing instant patch to equipments inputs and outputs for testing station components. Full front to back complete system freq response, distortion and RF linearity and spectral purity.This work completes the station construction. Most notable supriseis the implementation of a standard 4 inch VU meter in the audioTX feed to aid talking up the audio levels. Very old fashioned but very significant effect in obtaining consistent audio levels. A meter outperforms a bar of LEDS by a country mile. I think this is because of the vertical nature of LED bars over the horizontal behaviour of the VU meters.























Photo above shows: The 300watt HF power amplifier module from the Collins Rockwell HF-8023 linear amplifier under repair. 

21 October 2009.Collins HF-8023 PA Modules rebuild. Received the motorola bipolar proprietry helicopter ice cream cone transistors and refurbished two power amp modules. Found the performance is tolerant of mismatched transistors and -35db intermod was possible, in absence of the hard to find edge connectors, used hard wire to places on PCB board. Used muffin fans for cooling, and 20 watts of drive for the 300 watts output with 50 V DC supply around 12 amps.























Photo: Homebrew 200 watt MRF-175 motorola based HF linear amp under optimisation.

30 September 2009. Homebrew 400W HF Linear development. RF Output transformer design. While held up for Harris parts and HF-8023 power transistors. Both Collins and Harris projects are in limbo. Have been investigating the architecture and voltage choice for a 400 watt linear amplifier. Have settled on either MRF-175GV (28volt) or MRF176GV(50 V) gemini devices to parallel both halves and drive pushpull. These devices are available from obsolete 200 watt paging transmitters. ERG DSP6400. Workin progress involves fabrication of RF xformer assembly with semirigid coax and ferrite E Cores. Build difficulty lies in the stripping and bending template to produce a 1:16 (4turns) transformer in one piece.























Photo: shows fully assembled RF transormer

When bent and wound the semi rigid coaxwill produce accurate right dressed vertical stack that will be soldered as one mass. Have the stripped insulated sections in exactly the right alignment. Several attempts so far have not yielded a good sample. Once fabricated the RF xformer will be characterised at 400 peak ( 200 watts average) to gauge core cooling required.

26 August 2009. Harris RF-1110A linear amplifier driver module applications. Have been investigating the suitability of this plug-in for incorporation into home brew projects. Many thanks to NC4RY for his technical help. Can confirm this is a very usefull almost stand alone module requiring 100mW input for 100 Watts output. Has inbuilt ALC control stage, requires 50V and 5V supplies, cooling air, excellant conservative specs, linear response 2-30MHz. Most suitable for raising Collins or Harris exciters to practical antenna wattage. Driver module outputs 100 watts PEP. Will require two additional Harris power amplifier modules to output required 400 watts. Have one only.

09 July 2009. Collins 490T-1A tuner. Investigated compatibility problems when used with solid state100 watt amplifiers. Completed test interface and repair of control module and verified tuner as serviceable.

When connected to a 100 watt amp found insufficient power to drive tune modes. This was discovered to be caused by very high SWR offered by tuner in tune condition and subsequent amplifier power droop when swr's over 3:1 are encountered.

A 25 ohm resistor is inserted in series with tuner input to moderate SWR and loses 3DB of power but maintains swr at 2:1. The 490T tuner requires amplifiers of at least 200 watts to ensure operation or amps that can drive greater then 80 watts under high SWR's such as tube ones.

10 June 2009, Collins HF-8023, Harris RF-1110A, GRC-215 solid state amplifier progress.For 2 months have been collecting modules from above systems . Mentioned a long time ago was the interest in build a compatible amplifier system to attach to a HF-8010 exciter and have an RF output in range 200 to 400 watts.

The main engineering problem is having enough gain to raise 100mW to output power and some additional 10 db gain for feedback under ALC conditions and linearising the amplifier frequency response. It was OK to raise 10 watts drive power to the nominated output. The extra gain to use 100mW as the drive power was much harder. The GRC-215 modules are driven by a motorola broadband fat film IC for gain followed by pair of MRF-138 then followed by power splitter . The GRC215 modules are followed by a 3 port  power combiner, SWR sensor and low pass filter. The MRF 138 mosfets prototype GRC215 driving/gain stage  was breadboarded and used Phillips design information . Motorola publications were also used .


17 April 2009, GRC-215 HF Linear amplifier modules100 Watt MPA35875, part of team radio. Have been characterising these military surplus modules recently purchased from USA. They comprise motorola MRF-422 outputs driven by a pair of ACR20-28F helicopters, nicely made with a series of on board relay switched input attenuators since these module work with backpack radios. Need about 10 watts drive. A 35 MHz low pass filter is also on the module and means only additional banded LPF's for frequencies up to 15 MHz need be added. There is also a power sensor detector on both input and output. Connections are via two combination type D series connectors. Supply voltage for output stages is 28V and 12 volts for driver and bias supply controlwire. Not difficult to work out connections. These are good building blocks for different applications.



















Photo: AN/GRC-215 Modules in recycled heatsink during initial testing

17 March 2009, set exact shack position on satellite map.

9 February 2009 , Operated the AN/PRC-47 installed as 40metre mobile with modifications below over 800 kms return distance to Wyong Hamfest, NSW,and was impressed the way and how well it worked. The tactile nature of the operating controls allowed ops without looking from road. Antenna was 8 ft centre loaded whip. 24volt supply uses voltage doubler from 14 volt vehicle supply with shunt regulator and 24volt bank of 20 small nickle cadmium 6AH wet cells.(similiar aircraft surplus)


6 February 2009: Collins PRC-47,Found solution for insufficient gain reduction in 47 receiver when using radio set in mobile mode where car background ignition interference fails to be reduced in volume when reasonably strong SSB voice signal is received. The ignition interference is heard at same value as signal and is annoying and fatigueing . Also no volume ducking of noise takes place and the time constant of AGC appears excessively fast for SSB. The fix is simply to not set the AGC threshold as indicated in manual. But to advance it significantly untill a medium level SSB voice at say 100uV equivelent causes the background noise to be reduced in proportion. The end result is a better signal to noise ratio and a better time delay constant. Some experimentation of setting may be necessary. The time constant significantly improves and with much longer delay the RX base sensitivity will still unwind to hear weak stations when noise removed. When advancing AGC threshold it is necessary to reduce the audio TX sidetone control to prevent audio feedback with high front panel volume control settings. Both these ten turnadjustment pots are in the audio module.

PRC-47 thermal shut down in high power mobile transmit operation. Normal ham talking overheats the output tube quickly when ambient temperatures are over 28 deg centigrade. Duty cycle is quite low for standard radio. Fix: Add the TTY blower kit or own version.


7 December 2008: Harris RF-110A: RF-110A quiet air modification has proven successfull. Basically a two piece plenum box is added to the air filter mountings and 50 mm electrical conduit pastic parts are added to allow hose duct to be plugged in. 50 mm was only chosen for the sake I already had these items. It is 3 metres long. Blower mounted outside shack. At the feed end of the hose is a axial blower with an outlet of the same size. It is a high pressure type , the important feature is that it must have the same flow rate as required by the internal RF-110A fan. The function in this case is only to remove the suction pressure and susequent reduction in flow rate due to the input restriction at the input to the RF-110A. The RF-110 has no back pressure that can be measured. However it is important to leave the internal 110A fan operating as standard. This guarantees the turbulence cooling of the driver tubes. It would be more preffered to use a 100mm (4 inch) 4 inch duct hose and a high flow low pressure system then the one i have chosen. For normal servicing of the amplifier the duct is unplugged and unit tilts as normal. In late December i will look very carefully why its difficult to cool the the driver tubes.


18 November 2008: Collins Rockwell HF-8010 exciter, USB/LSB RF output power unbalance. This problem affects 8010's equipped with early model LSB TX IF cards. There is no third pot for adjusting LSB channel gain fitted. Procedure asks for emitter resistors to be changed. Be aware this can happen.Hint: If used in the ISB mode use the compression threshold 10 turn pot in the LSB audio channel to set a higher or lower operating point to gain the LSB RF output power balance with the USB channel.Use the same audio drive signal in both channels for this adjustment.


30 October 2008: Harris RF590, RF-1310, RF-2368URR, displays problem. Spent time investigating the problem in Harris receivers and exciters where the displays are dim and difficult to see. In this case the RHS numeric frequency display. Acting on information from VK5ABN I obtained a sample 11 digit vacum fluorescent display D0111LT-33-1101($US22.60) from Newhaven Display International, Elgin, IL. I found it pin for pin compatible and directly interchangeable with the OEM Futaba taiwan 11-LT-02Z display. Previously I had tried unsuccessfully boosting the filament voltage but was not able generate a elegant modification. The new display works fine.





















Photo: Harris RF-130-02 system during refurbishment.




























Photo: RF-110A linear under repair























Photo above shows clockwise from LHS : Harris HF RF-130-02 system audio and facilities patch panel  ,ham shack antenna interchange panel ( basically a 4 by 2 coaxial switching matrix)  , 50 ohm dummy load and Sierra thru line wattmeter


17th October 2008: Quietening Harris RF-110A amplifier, results of efforts. Major issue identified for applying external air is providing sufficient cooling to driver tubes. The positioning and high velocity flow pattern of the internal fan has a little black magic in driver cooling. (200 watts heat from DC input to the 8122's).Various schemes with plus/minus tried.

1)Suction , internal fan still installed , blower fan fuse removed,low noise, (driver tube cooling probs)-no vane switch operation-eliminated as solution.

2) High volume (90mm diameter duct)low pressure since almost zero RF110A back pressure -remove internal 110A fan (driver tube cooling and vane switch problems)-internal powered fan needed- eliminated as solution.

3) As above with internal operating RF110A fan--OK (requires remote supplementary fan to overcome extended duct back pressure, noise level OK if attachment box has sound deadening material--- definate potential solution

4)High pressure 160cu ft/min delivered by 50mm diameter tube to attachment plenum chamber to RF-110A , internal 110A fan as installed and not powered, adequate airflow , however driver tube cooling probs. Low noise, internal vane switch works OK. --driver tubes lack cooling- eliminated as solution

5) High pressure , system as above , however internal fan left energised as per normal standard RF-110, driver tubes satisfied as per normal, with sound deadening material in plenum adapter box (50mm flexible tube to RF-110A )high pitched scream is eliminated and low level waterfall acceptable air noise is present. This noise suppression system adopted.

6)Useing Harris blower noise supression kit, RF-110A operating noise level is reduced but not as effectively as in (5), still high enough to wish for more supression when within 1 metre of microphone-solution if amplifier is remotely located.






























Photo: RF-110A Amplifier with external air modification. 160cu ft min delivered through 2"diameter tube. Almost zero back pressure.


13 July 2008: HF80 tantalum capacitor failures,Investigation results. Purchased 100 NEW 10uf 35 volt bead tantalum capacitors , NOS (New Old stock) identical to those fitted to HF80 series collins, with exception have a higher operating voltage. Collins units are 25 volt working. Applied 24 volts once only to each capacitor with 3 amp current limit. Nine capacitors immiediatly went short circuit/low impedance of 100 tested. Carried out the test cycle a second and third time, no further capacitors went faulty. The result of this test is 1) Only the faulty capacitors need to be changed when repairing 80 series.( there may be no benefit in widescale replacement). 2)The failure mode can occur at random also with new replacement capacitors. Power supply series source impedance and random effects not identified are responsible. 3) I recommend test all NEW replacement tantalums before fitting to 80' equipments.

11 July 2008: Repair to component level HF80 series Synthesiser decade divider cards. In each module at least one tantalum and possibly burnt out 100mH axial inductor to replace. They can be any of the several fitted. Found with ohmeter. No other faults found. RF adjustments found to be stable and alignments not required.

08 June 2008: Repair work continues on 80 series modules to component level. Mainly HF054A IF amplifier cards. The five slug tantalum capacitors closest to edge connector mostly the cause of failure. Once repaired the signal alignment of the card is tedious but well worth the effort. Care is needed with upsetting the signal zero indication of the s- meter as a side issue. Advise marking of pot settings in case a return to original setting is required.























Photo: Collins HF-8010A IF card repair
























Collins HF-8010A under test


















Photo: Exciter under test with remote control.

13 April 2008: Continously working on repair of Collins 80 series receivers and exciters. HF8014, HF-8010, HF-8054,HF-8050 chassis cases reconstruction. On test the same tantulum electrolytics on cards or under synthesiser tray cause problems in most units tested. Only about 10 capacitors responsible for the no-go conditions. Very few faults found in cards outside these semi shorted and shorted caps. PCB's exported to other radios found to be fully compatible without needing any tuning for that serial number. On multi channel receivers it possible to have different IF gains when mixing PCB's. Just a few pots readjustment can rectify. Rather then carry out a full alignment. However module extenders are required.


4 March 2008: Harris Amplifier RF-110A blower noise quietening tests. The idea of suction on the outlet side was investigated and despite equivelent airflow at the intake filter the vane switch failed to operate. It was discovered the the vane switch is placed in the narrow region hi velocity windprint of the blower. This represents a unrealistic and overlarge airflow if this switch is to be activated. The concept OK but will need vane switch disabling, and pressure drop differential metering across the 1500B's controlling the protection. There still remains the problem of insufficient air turbulence to cool the driver tubes.

A interim arrangement has been found satisfactory. A supplementary add-on ducting system was used to muffle the normally radiated sound. A square to round intake converter is used with small plenum box that bolts onto filter screws. A 100mm flexible tube of three metres (3.6 feet)length. The cooling air end is connected to a 50Hz cockleshell spiral blower (150 cubic feet minute/3inches water gauge) to overcome frictional losses of the corrugated tube. The closed system at the input area of RF-110A suppresses the noise considerably. When servicing this auxiliary system is disconnected to restore original noisy configuration.

28 February 2008: Commenced pre-installation testing of The Harris transmitter system comprising RF-110A,RF-1310 and RF-124. The blower noise problem will require solution before Ham ops are possible. Some work although not complete was done on this. Report to follow.


03 February 2008: Collins HF8050 series recievers , tantulum capacitor failures. Have concluded nearly all tantulum failures are confined to only those on the lowest impedance connection to powers supply +24V,-15V, +15V rails. Have found failure is manufacturer component specific and age related. Typically and repititively around 10 failure sites in RX, Tantalums with series resistors will be totally reliable. Recommend running long stored receivers at half mains voltage for at least 10 minutes before full voltage application. Continueing the working bee on equipments to replace an/trc75.


29th January 2008. Mobile Power Loss: optimum thru vehicle holes size to minimise capacitive losses is confirmed at 75 mm (3 inches)diameter. Useing a thermo-ammeter on both sides of the feedthru shows less then 10% loss. A 12mm( 1/2 inch) hole bush loses 90% of power for hi impedance (approaching 1/2 wave) whips fed thru vehicle walls even with short pigtail.

12th January 2008 Rockwell Collins 80 series versus Harris. Testing of various components of both systems is continueing.

Comparison was made between Collins HF-8050A, HF-8054A, HF-8014A, 548L amp series and Harris RF-590, RF-1310, RF-110A, RF-124 equipments.

Both equipment series have technical strengths, excellant documentation and use generic parts extensively. The Harris system items have more compact integration and ham applications friendliness. Additional more modernistic features.

Under construction is a Harris RF-130-01 transmitter system to supplement the AN/TRC75.


A few observations were made during this work while working on the RF-110A.

RF-110A Blower Noise: Confirmed is the blower noise problem. Three approaches to be explored in early Feb 08 when equipment commissioned. 1) A longer intake muffler using Hemholtz resonator design for notching out dominant noise frequencies. Simply removed for servicing RF-110A allowing amplifier to reamin stock dstandard. 2) Use blower in suction mode on out-take side of linear to create negative pressure and equivelent airflow at intake. Remove power feed to existing blower, leave to free wheel. 3) Reduce blower speed during Receiving time by PTT control of blower power . Reduce phase voltage in receive mode.

The bane of the RF-110A is by popular consensus and I agree is the level of blower noise. Lower noise solutions by others compromise the service tiltable access. Alternative air systems may need to reinstall the original blower for troubleshooting duration.

Early URG-1 Collins 1KW tube amplifiers such as the 548L-4 were cooled by suction rather then be blown from intake side.


ON-AIR voice personalities. Harris VS Collins. Collins definatley has a distinctive natural subjective sound whereas Harris has a unique but good quality due to the very active audio digital processor . AGC equivelent action is over 35 db of average gain held. Harris has considerable talk power . Scale distortion is an issue for those who may prefer a laid back sound.The Harris average transmitted SSB power is greater then the Collins system by at least 20%. Does work very well and shacks using harris systems will need quiete echo free rooms or some form of microphone gating.Harris RF-1310 exciter has no provision to control the voice processing density .Both transmittersystems of Collins and harris test less then 3% total harmonic distortion tested micrphone to monitoring receiver output.

To get control of the modulation density in RF1310/RF110A :Set ALC and AGC as normal set-up in menues. Assumes exciter output attenuator set to 0 db. The input gain preset controls near panel meter are then used to reduce the compression range by reducing the amount of audio fed to the exciter. For instance in SSB mode if 0 db is set on meter then a minimum of 35 db compression will be realised. For every db of reduced input by reducing the preset then a coresponding amount of compression will be reduced. Reduce input by 20 db will produce 15 db of processing. Recommending set up of audio to -15 db on panel meter. This method also helps with the amount of background shack noise that is brought up between words when useing desk mic.

20 December 2007 The solid state amplifier project will go on hold until ham station upgrade takes place. Have received the 25 ohm coax from the USA and have started work on the RF transformers for the motorola 400 watt amplifier. have done some work on the PCB and heatsinking and copper heat spreader.

08 November 2007 A quiet month for fabrication of RF projects, VLF 16KHz transceiver-dropped for time being,75 mm hole not drilled thru Kombi yet till make suitable perspex plate, 490T project deffered untill get another tuner. New project concept started up to build a solid state HF amplifier into a Harris RF-110 case to clone a Harris look alike and do away with the R-124 power supply (90KGs). Have purchased all the major parts motorola MRF176GV geminis, Communication concepts supplied ferrites, 25ohm coax, copper spreader,heatsink system. Will build breadboard version of amp to check stability and efficiency. (note added 18 June 2011: have been unable in ensueing time to obtain a second Harris 300 watt PA module to complete this project and has remained in archive.)


10 October 2007 Have been concerned for some time the poor on air mobile performance of the VW setup. Always getting poor 20 km (5,3) reports. Despite increasing power to 400 watts. Found the vehicle feedthru stray capacitance is a serious issue and have moved to increase the hole size to 3 inch diameter from 3/4 inch previously.

Led me to investigate just how much losses of transmitter power take place when useing antenna tuners inside vehicles with outside high impedance whip antennas. In this case the feeder from tuner to vehicle wall was 10 inches. Conducted a series of experiments on the VW kombi with a 3/4 inch porcelain bush thru the wall. I determined by experiment 20 db of power loss was present meaning if 1000 watts transmitter was used the power available to the whip base was only equivelent to 10 watts.

Photo: Harris CU-2397 tuner installation, note large hole based feedthru. Reasons explored in text.


















Photo: Finished modified feed thru with modified diameter FFR AN/TRC-75 AT-1011 candlestick antenna base. Insulator material is delron


Feedthru in service was a common type used for light aircraft hf radios, approximately 5/8th diameter with 3/16 inch threaded centre.

Measurements to the installation were made useing a RF thermocouple ammeter connected to both sides of the feedthru insulator. On one side the thru insulator showed high current(say 100%) and (10%) on the other side. By leaving the back hingeing door open and running a short feeder link around it was found the RF current was 100% all along the link and arriving at the whip base.

Further consideration indicated the minimum vehicle hole diameter to reduce these losses to reasonable level was 3 inch diameter. My conclusion is losses due to excessive stray capacitance can be huge. In this case would of needed a 10KW mobile transmitter to be equivelent to a home 100 watt rig on a dipole antenna. See photos above


14th August 2007. Had the honour of visiting briefly the BB63 Missouri radio room in Pearl Harbour. The radio room central and equipment racks were impressive and seeing the extensive Harris and General Dynamics equipments gave me a good idea of their interconnections and associated systems and just how the Navy fitted their pieces together. Gavean incentive to aqquire Harris equipments.

The work underway there is to concentrate the Harris equipments in closer proximity. The noisy blowers was quoted as problem. Maybe the 3400 watts of heat a RF-110A can put in a room maybe another.

I got some good ideas and thank the volunteers for their selfless efforts in making the radio room as truly representative of the mighty "Mo".


09th June 2007: VK2BLC Station: Completed maintenance of the TRC-75 equipments. These have been in continous use and used as the only VK2BLC  transmitter since 1978.

Primary station transmitter is the Collins AN/TRC-75 modified , pictured below. Main modification is (1) the internal blowers were removed and the manifold is fed with external air to a pressure of 4.0 inches of water gauge. (2). The internal whip series inductors were disconnected and the coaxial cable run right thru to the rear of the internal antenna coupler, the CU-749 becomes then just a transmatch. A n type barrel adapter feeds the RF thru the cabinent, The porclain cabinet feedthru was removed and replaced by aluminium plate fitted with barrel n type feedthru adapter.(3) The T-730 linear amplifier is modified from 100 watts to 400 watts PEP by changing fixed resistor value behind the TRC-730 front cover. When in lower power position , the cabinet power switch then selects 400 watts or 1KW. The power control is visable as the red lockwired toggle guard above the  cooling air pipe. The lower AN/TRC-75 CY-2600 cabinet is a later build.

























Photo above shows: TRC-75 (1961) Transceiver pair, early and late model CY-2600 cabinet. Photo below is the USA issued 28V DC input 400HZ 208 V 3 phase output PP-2352 inverter as used in AN/MRC-87. This DC powered inverter was not used by the Australians.














































Photo: Collins AN/TRC-75 T-7309circa 1961) 1KW Linear amplifier, 50 years old, 3 eimac 4CX250R final tubes, phase tuned , inbuilt 1.3KV power supply. Photo taken 2007 during maintenence .
































Photo above shows: AN/TRC-75 transceiver in use in the AN/MRC-87 mobile installation. Acknowledge collins collectors Association as source of MRC-87 image.

Photo: Homebrew AN/TRC-75 remote control unit utilising 651-E duplex rx VF panel.Inside behind the panel is a dual amplifier electronics group also salvaged from the 651E which comprise 2 by multi output impedance 10 watt amp;ifiers and 2 mic audio amplifier compressor modules.
























Photo below shows: homebrew AN/TRC-75 support test fixture January 2012 used to align and test CV465 synthesiser A2 IF amplifier discrimminator modules IF assemblies card. Creates a adapter that interfaces with the AN/URM-124 module test set.















































Photo: Collins AN/URM-124 AN/TRC-75 module test set fitted with homebrew A2 IF sub-assembly test fixture adapter and fitted with IF assembly card ready for testing.





















Photo above shows current photos of a archived Homebrew 400 Hz frequency changer  built in 1979 used to power original AN/TRC-75 installation. 240 volt , 50 HZ 2KVA input. This static frequency changer replaced the original Jatz and Heintz 2,500VA 400hz  rotary converter operating from 28 volts DC. That inverter was sourced from RAAF surplus from  Hercules aircraft.




















Photo above shows : interior of homebrew 400hz frequency changer. Uses a extensively rebuilt parameters VSD  (variable speed drive) from recycle , powers supply and frequency generation circuits redesigned for 208volt and 400hz and output  isolation delta wye transformer added. 

Collins AN/TRC-75 (circa 1961)AN/TRC-75(28,000channels).

The TRC-75 is capable of high end SSB specification. More specifically the T-730 linear amplifier is easily capable of better then 40db intermod at 1KW two tone 3.5 to 28.5 MHz utilizing 4CX250R/7580W tubes and requires only 100mW RF drive. When reduced to near half KW amplifier is basically distortion free.(45 db intermod). 4CX250B tubes can be readily used and RF power falls to 900W for in spec performance. Linear amplifier automatic tune time is less then 1.5 sec. Cooling air flow is 60CFM at 4 inches water gauge. The R761 receiver features similarities with the R-390A in performance. A low rx noise floor, and yields better then 0.15uV with sig noise of 10 db for all frequencies between 3.5 and 28.5 MHz given selected AM1528 modules. Frequency accuracy is better then 0.1 part in 10 to six. Total audio system distortion is less 1% ,180 to 3500Hz at full reference modulation. Typical audio/ALC behaviour is mike compression 15 db at 20:1db, linear amp negative feedback 10 db, ALC typical at 1KW is 17db.The AN/TRC-75 has 14 mechanical filters, 6 servo systems , 46 tubes , 97 transistors, many diodes , 3 independent IF amplifiers,demodulators and audio systems. Control head is a digital to analogue converter and one section connects 39 resistors in 4,000 combinations.

Harris RF-590 HF Receiver: A Harris 590 HF reciever is used as a spotting Receiver in Dubbo.This is to overcome the slow tuneing time of the TRC75 servo systems when looking for stations. Ham bands are searched quickly and the exact frequency read from the 590 and entered into the TRC75. Takes up to 20 secs to have the trc75 system tuned and auto antenna tuner satisfied.

A 50 ohm splitter is used at the R-761 RX input to gain a RF 590 feed.

7th May 2006: VW Mobile Installation: Transportable equipments in Perth are Transworld TW1000 system installed in Kombi van. 28volt DC current drain is 0.8 amp RX and peaks 50amps for 400 watt SSB output. This far superior to the previous AN/ARC102/618T system used previously. At 28 volt on RX,12 amps and on tx peaks to 60 amps.

































Photo: Collins AN/ARC-102  Collins 618T Original VW Kombi ham mobile 1987 to 2005 at time of teardown. The 618T installation utilises the HF control head and the powered speaker form the AN/MRC-95 vehicular mounted 618T. The lower two homebrew panels on RHS are the general ancilliaries like swr senser head LHS panel and homebrew full radio DC and Audio interfaces on RHS in box format. The 180R-6 coupler control a C-2848/TRC-75 for the rear vehicle mounted coupler is mounted under the 618T transceiver.



NVIS Experiments: Experiments in late 2006 were in areas of NVIS using magnetic loop and close to ground dipoles.Took atvantage of current low sunspot cycle MUF for 90 degree high angle tests. Can confirm NVIS is very successful but requires quiet vehicle since the highly dispersed and uniform field strength is around 30 microvolts for approximately 0.4KW antenna drive.Conducted tests from ground zero to 700 kms without zone of silence. If vehicle noise is 10uV then 100uV signal is required to produce 20DB S+N/N.

Conclusion: Insufficient ham frequencies exist between 4 and 9MHz to make ham NVIS feasible. When tied to a NVIS frequency table and 100 watt powers, frequency changes are hourly. A frequency allocation in the 5 to 6 MHz band and 8 to 9 MZ band would help significantly. Confirm path loss roughly 110 db.

Loop photo below was constructedfor the NVIS experiments.





























Photo: Homebrew loop under construction vac cap, 20 to1500pf 15KV.






























Photo: Transmitting one metre loop, 3.4 to 10.2MHz , rated400 watts, gamma matched unbalanced feed. Pneumatic mast. Adjustable height allows different modes. EG, NVIS to normal ionospheric. In shack wall photo at top bio the mast base section and control box can be seen

It was found neccessary to add a simple whip ground plane below the loop to preserve feed impedance as antenna is raised to any height. Can be seen in 3rd photo down from top of bio.


10 April 2006: Transworld VW installation: Currently working on the transworld TW100/TWA1000A transceiver amplifier combination in the Kombi van in Perth, still trying to interface a collins 490T 1A antenna coupler to the TW system. The 490t tuner repairs have been completed Interface is under construction. In meantime have deployed a miller AT2500 auto/manual high power antenna tuner as tempory measure. The systems are 28V DC based and required the addition of another alternator and battery. That is completed along with the mounting of TW100 near driver and TWA1000A in separate rear rack and some cabling.

Some initial testing showed the ability of the miller AT2500 to work mobile and tune with 10watts CW. Will not operate with short whips (12feet) however and requires the 15 foot whip, this can be bent over from Kombi rear to front.The metering on the Miller is excellant and strong point of this 2KW tuner.

The AT2500 tuner is working satisfactorily with 32 foot whip (AT/1011) and progress is steadily making ground on the 490T tuner interface. This task is proving more difficult then expected due to low current fan-out from the TW100 for the auto ATU function.



Photo below shows : VK2BLC aged twelve, 1957,  with first transceiver. A No 19 set, war surplus from National Radio, Sydney , Cost then was 8 pounds including shipping (FOB), saved up from doing odd jobs. Mowed quite a few lawns and rotary howed vegetable patches  for grandfather to pay for battery charging to use it. Sitting above the No 19 is a Fullerphone , the very first piece of military surplus owned. (ten shillings) and introduction to morse code. 




























8584667 Last modified: 2018-01-16 13:19:12, 466083 bytes

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