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KB4ABE USA flag USA

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Kindest ham radio greetings from Tampa, Florida. My interest in amateur radio for the last 40 years has been VHF and UHF operating with my first HF station on-the-air December 30, 2013! Previously I worked HF contest stations for W4DFU (University of Florida,1982).

Current interest in weak signal propagation especially on 6m using FT-8. Special thanks to Joe Taylor for all your efforts to improve the art of radio.

Profession: Electrical Engineer, Magnetic Resonance Imaging (MRI), service engineering support for clinical and research systems.

 

HF Antenna - "Long" Inverted L

I find the Long Inverted L antenna together with the SGC-231 tuner/antenna coupler to be an ideal backyard HF station. It is oriented E-W and fed at the west end of the downward part of the "L" at about 4 ft above elevation.

A non-resonant antenna length and excellent grounding/counterpoise system at the feedpoint (with longest ground counter poise located below horizontal antenna wire and grounding conductor bonded to household grounding electrode and cold water pipe) gives reliable HF performance.

EZNEC plots support my on-air findings with low angles/multi-lobes for 10-20m for DX, and more (cardiod upward) NVIS (Near Vertical Incident Skywave) pattern for 30-160m. Note: NVIS daytime coverage on 40m is solid 400-500 miles operating radius, while NVIS evening coverage on 60m-160m out to 800-900 miles. 30m coverage is mixed DX and NVIS.

Polarization is mixed horizontal and vertical.

Use of the SGC-231 antenna coupler allows for fast band/tuning changes for digital modes such as JT65 and FT8 from 160m to 6m.

 

 

Details and Dimensions for my "Long" Inverted L antenna as follows:

Grounding Electrode: 5/8 inch x 8 foot galvanized rod, driven 7 foot 9 inches into soil adjacent to one of the vertical supports below the antenna coupler.

Ground counterpoise (located below horizontal radiator): 62 ft - buried 3-4 inches, 12 AWG one end bonded to grounding electrode, the opposite end is open.

Vertical ground conductor: 4 ft, 6 in, 12 AWG, one end bonded to grounding electrode, the other connected to SGC-231 grounding lug (see grounding below).

Vertical radiator: 8 ft 6 in, 12 AWG, one end connected to SGC-231 via grounding relay, the other connected to horizontal conductor at 13 ft elevation.

Horizontal radiator: 57 ft, 12 AWG, ceramic porcelin insulators, driven end connected to the top of the vertical radiator, supported by 2-4x4x16ft poles pressure treated, painted and anchored with a poured concrete footing.

Comments:

Antenna Length: I believe the ideal non-resonant length would be about 71 ft total, 57 ft horizontal, and  14 ft vertical, at elevation of 16 to 19 ft. The vertical length/elevation should be selected by the operator to give optimal vertical pattern response for 6m (0.5w to 3/4w), or 10m set for (0.25w to 0.5w). Note: due to real estate constraints I was not able to achieve goals.

SGC Elevation: SGC recommends a maximum elevation of about 5 ft above the ground surface. I have found good results with an elevation of 2 to 5 ft with different antenna/grounding configurations including a sloper (sloper gives lower angle).

SGC Enclosure: The SGC tuner must be housed within a suitable NEMA rated non-conductive enclosure as shown for protection and the antenna lead protected (high voltage potential) from accidental contact (see CANTEX, 24"x24"). These are available from Lowes, Home Depot or local electrical supplier.

Antenna Conductor: The antenna was constructed using #12 AWG copper, THWN/THHN 19 mil insulated wire due to short length and limited sag. In the future, I may consider replacing the copper conductor with an insulated copper plated steel stranded wire of same diameter.

Antenna Conductor Insulated: I believe the benefit of an horizontal insulated antenna conductor helps minimize static charge build-up and helps reduce overall system noise especially below 60 MHz and HF.

Antenna Lightning protection: The antenna must be grounded when there is lightning probability or static discharge/induced currents that could damage the SGC231 tuner or station. This is accomplished by using a relay located at the SGC 231 antenna connection which grounds the antenna and isolates the SGC231 when 12VDC bias is removed. The relay has not affected tuning or signal radiation as might be suspected. The SGC231 coaxial feeder is further protected using a shunt 600V gas discharge arrestor (see L-COM) which passes DC bias and ground bonded to the service entrance electrode just prior to entering the radio operating location.

Antenna Grounding: Later I added a grounding conductor bonding the antenna electrode to the home service entrance electrode and cold water pipe without any measureable increase in system noise or signal pattern distortion. This was done to minimize any voltage potential (lightning flash-over) developed from the antenna to radio system power ground. Additional tests have shown excellent results when bonding to a cold water well-head pipe (if galvanized steel) if no other grounding radials are readily available. Use the proper methods of attaching to either grounding electrode or cold water pipe (rated bronze nut or clamp). Review NEC electrical standards prior to connection if you aren't sure.

 

SGC-231 antenna coupler, SGC DC Bias Tee, Antenna Grounding relay, Fair-rite clamp-on common mode RFI (ferrite) suppressors (NOTE: a coaxial balun coil may be more effective) mounted within Cantex NEMA non-conductive enclosure. Feed coaxial cable is LMR400-DB.

Antenna DX directional pattern:

The "Long" Inverted L seems to favor E-NE, and E-SE directions (Especially Central Europe and Central Asia) for 20, 17, 15, 12m and this is supported by the EZNEC plots.

I plan to add a 2nd inverted L or sloper oriented at 90 degrees (N-S) to the first to fill a percieved signal void (switched by relay).

The station is an ICOM IC 7410 normally operated at about 80 W PEP.

 

WSJT-X, Sporatic E and 6m.

Poor HF conditions gave me incentive to investigate weak signal propagation.  WSJT-X with FT-8, or JT-65 seems to be the answer when solar sun-spot activity is at a minimum. Hence the need for a 6m omni-base DX antenna... Squalo or J Pole? Transmit power limited to 30W PEP.

6m J-pole antenna

Electrical radiator 0.5 wavelength to matching 0.25 wavelength seems to have worked very well (see tuning photos attached). DC ground is needed in Florida for lightning protection. All copper pipe construction (1/2 & 3/4 inch) soldered together. NOTE: most difficult to keep straight alignment of mounting support stub while soldering. Coaxial cable is LMR240 at feedpoint with 1/2" wide brass straps to copper tubing. Greatest mechanical support to attach coaxial sheild and cable strain relief (UV PVC) to 3/4" tubing and center conductor of coaxial cable (lug) to 0.25w stub (using brass straps). A 1" x 7.5" x 0.125" G10 plate (2- 70# UV cable ty) is used for mechanical support from main radiator to 0.25w stub (44" from tee). A threaded adapter (1/2"-3/4") is used to connect the 1/2" upper tubing (67") to the lower 3/4" tubing mast (98.25"). Coat copper tubing suface if corrosion protection is desired. The coaxial cable must be connected to a means of lightning suppression prior to entry into the station.

Using network analyzer or antenna tuner set the impedance at 50 ohms (sliding the feedpoint brass straps), record return loss, and VSWR bandwidth. Field azmith measurements indicate omni-directional pattern.

Dimensions (inches) at design for 51.5 MHz:

Section     Length     Description

A               165.5       1/2"(67") + 3/4" (98.25") tubing (0.5w radiator & 0.25w stub)

B                55.75       1/2" tubing (0.25w stub)

C                5.125       1/2" tubing (horizontal) about

D                5.375       1/2" wide brass strap (interior dimension, feed point location)

E                21.5          3/4" tubing (mounting stub)

 

 

 

 

ICOM 7410 - USB interface to host DELL laptop

First load download to host (laptop) ICOM USB driver... see ICOM web.

A USB 2 hub needed for this interface connection - see ATIVA (MH701) or similar 4-7 port hub (USB2/3). USB cables longer than 6 ft will likely not connect reliably if at all.

WSJT configuration -- see web for general settings. Use PSK reporting -- this is web DX link to monitor your logged receptions and what stations are receiving your transmission.

https://pskreporter.info/pskmap.html

WSJT/ICOM 7410 specific: Radio > COM4, 19200, Data 8 bits, Stop 1 bit, Handshake Hardware, PTT CAT, Mode DATA/Pkt, Split Rig none. Audio (DELL) Input microphone (3-USB Audio CODEC), Speakers (3-USB Audio CODEC) - mono. Configuration Tab - Clone and name to save settings including TX Macros and personalized messages.

WSJT Operating notes:

1. Rx Gain for ver. 1.8 the RX gain slider located on the left lower side is non-functional. Set the WSJT slider to minimum, then adjust radio reciever RF gain levels to "green" (20-70 dB) as seen on the WSJT left sider. Version 1.7 seemed to work well but is now disabled.

2. Decoder must synchronize -- the PC must be frequently synchronized to INTERNET or Coordinated Universal Time (UTC) for message decoding. Remote location without internet access may use MultiPSK Clock function to sync to WWV or other broadcast time source. Windows 10 users connected to the internet>right click on time and date in task bar>adjust date and time>add clocks for different time zones>Internet Time Tab>Change settings>check box sync with internet time server and select time.nist.gov>update now>OK.

3. Use of the antenna coupler (SGC231) requires using the WSJT "TUNE" tab to set for minimum VSWR at nominal power levels (20W, in about 4sec).

4. Set the ALC to 90-98% with Radio mic-gain or WSJT Pwr slider on right side while in "TUNE" mode.

5. When a QSO is complete with sending of 73's, log this to QRZ logfile immediately.

 

ICOM 7410 configuration settings:

Menu SET button (hold 1sec).

38 - USB audio SQL -- OFF (OPEN)

39 - USB MOD level -- Default or 50%

40 - DATA OFF MOD -- USB

41 - DATA MOD -- USB

42 - CI-V Baud Rate -- 19200

43 - CI-V address -- 80h

44 - CIV Transceive -- ON

45 - USB Serial Function -- CI-V

M1 - AGC OFF

Filter F1 - BW 3.6KHz important to set at widest BW

Preamp 2 for 50 MHz

NR about 40% of full

Transmit power 5-30 W, with ALC (Mic gain) at 90-98%.

JT65/FT8 operating: alternate from even to odd minutes to detect ALL stations and remember only 13 characters/message including spaces. Messages are short - CQ, callsign/s, grid location, Rx signal report exchange and 73's. WSJT provides logging of ALL signals decoded so watch the size of this file. When responding to a CQ, you must Enable TX and quickly click on the call sign prior to the next cycle JT65-56sec+4sec (60sec), FT8-13+2sec (15sec). Because of the quick response of FT-8, automated responses of signal exchange, RRR, and 73's are typical.

 

UHF and 6m repeater/s

The VHF/UHF repeaters shown below are part of a radio system covering the TAMPA BAY area including Tampa, St. Petersburg and Clearwater. 

They are networked (Allstar, Echolink and DSTAR) into the KA9RIX (arsrepeaters.com, Clearwater, FL) repeater system (VHF and UHF) with coverage extending along the west coast of Florida.

The 6m Motorola Micor FM repeater (under W4HSO call sign) is used mainly for local and some DX with highpower (330W, using 2-8560AS Eimac PA) transmitter and groundplane antenna (DB-201) at 200ft. The 6m repeater output is 51.64 MHz/PL 141.3 Hz, primary receiver at 51.14 MHz/PL 141.3 Hz. Six meter FM is limited to mobile and fixed base use. Urban coverage is limited by noise and path loss.

I have included analytical measurements of the Decibel Products DB212 antenna for those interested in the "hairpin" design used in many DB antenna designs (Note the approximate 50 ohm input impedance of the single loop). This impedance is critical to design of multiple element phased arrays and transformer cables. The DB212 must be installed against a vertical metallic mast for this design impedance.

Please QSL via QRZ log.

Ciao and 73's,

KB4ABE

 

 

KB4ABE VHF/UHF repeaters

 

 

DB212 hair-pin dipole antenna response shown below.

 

 

8391189 Last modified: 2017-10-15 21:25:05, 14721 bytes

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