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VK2EVB Australia flag Australia

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Ham Member Lookups: 8022

 

After getting interested in crystal sets as a boy, and progressing to valve receiver construction,I then repaired valve radio and BW TV receivers as a hobby in early teens. My father an Electronics Technician and Amateur fostered this interest with a supply of the appropriate parts and scrapped equipment.Obviously I was interested in ham radio but unfortunately I didn't try for an Amateur Licence until later in life once I had settled in a career.

My callsigns have been, Novice VK2VRO, Limited VK2XPJ and my present Advanced call sign VK2EVB. Main interests are Home Brew, Digital Modes, QRP, amateur satellites and portable operations. I get distracted by computers, PCB and circuit design, antenna design and the development of headaches of one sort or another. These days I take things a bit more leisurely, settling for a Gap Titan DX vertical, A T2FD terminated dipole and some VHF/UHF satellite antennas.


I started DSTAR in 2011 with an Icom ID-31A DStar transceiver with built in GPS and set up a DStar HotSpot with my son's help. Intitally ran well as VK2EVB B 438.925 Mhz on a Raspberry Pi computer with a USB soundcard and GPIO PTT, with a 5 km range. Now using a DV RPTR V1 modem instead of a soundcard.  Christmas 2015 saw me buy an ID-51A+ dual band DStar transceiver which increases my capability to VHF when travelling and is performing very well. I use it for walking or travel these days leaving the ID-31A as a shack monitor rig.

Usually logged onto DCS028Q or DCS001C.


Using a Yaesu G-5500 rotator system for my satellite interests.A FoxDelta ST1 computer interface controls azimuth/ elevation, and it works very well. With some homebrew antennas I can now use the system to full advantage with tracking and antenna control software. An Icom IC-9100 has improved operations as well. Now working on 23cm antennas.

 

+ 23cm up and running now and quite pleased with setup +

+Just turned the 2 mx & 70 cm yagis horizontal to enhance terestrial propagation.+

 


APRS got me hooked so I built some kit Trackers including FoxTrack, OT+ and more recently a Tiny Track 4 which runs a fill in digipeater VK2EVB-1. I enjoy using a Yaesu VX8GR and take it most places even to Vancouver BC Canada on Holidays. What a great little transceiver and so versatile and easy to use.

I built SMD inverters to convert some TTL GPS's to serial to make them compatible with my trackers.


I have been working digital modes like PSK31 for years but recently tried FreeDV on HF with surprizing results. I am still rather pleased with my GAP Titan DX and the excellent results on DX but the noisey local environment is hampering my efforts. I have purchased an MFJ-1026 noise canceller which takes a lot of adjustment but does actually work and reduces noise from local household by a large amount. Unfortunately every time I move up or down a band or change bandsit requires re-adjustment which is not too bad for digital modes but gets to be a tiresome chore with SSB operation as the adjustments are so fine. I am becoming convinced I need another antenna (NVIS) for local working on 40 & 80 metres. 

I also built a VK5 Antenna analyser kit which went together very well. Once completed and tested I extended the coverage to six metres. This has been an invaluable tool in my antenna experiments and works very well. A very satisfying project. http://www.ahars.com.au/htm/jst_aerial_analyser_kit.html

 

 

I am currently building their latest offering (December 2015) a VHF/HF Aerial Analyser which provides coverage from 1.5 Mhz up to 170 Mhz. More to follow soon.          http://www.ahars.com.au/about/kits/                                                                                                                


 

I still like operating portable with my FT-817ND and my W3FF portable dipole clone when I get the chance. Lots of fun has been gained from this small but surprizingly effective combination and special thanks goes to W3FF for his webpage of instructions. With a bit of patience I developed a tapped multiband 6mx, 10mx, 15mx, 20mx & 40mx version with 80mx add on coils. Plans and construction manual available from Ozipole yahoo group.

 

 

 

 

 

 

https://sites.google.com/site/w3ffhomepage/homebrew-buddipole-plans  https://sites.google.com/site/w3ffhomepage/new-homebrew-buddstick-plans


​Magnetic Loop Test.

I have been playing with Magnetic loop antennas, again, but this time I am using 16mm copper tubing as the radiator. The results on 40 metres have been impressive using my IC-703+. The major advantage is the drop in noise level compared with  my dipole or GAP vertical. Having a drop from S 5-6 to not registering on the meter is brilliant as I can hear QRP stations. Starting with a motor/gearbox from our local Jaycar Electronics store to drive the 150 PF variable capacitor I found the speed of rotation much too fast. A pulse width modulator circuit seemed the thing to use to gain better speed control so a test circuit was built onto a solderless breadboard. While it did prove better at lowering the revolution rate it also made apparent the problem of motor over run once power had been cut off. Really a lower gear ratio is needed to give more control.

After having a stepper motor controller demonstrated to me I now feel that is the way to go as it is far more accurate.

More to come.

 

 

 

 


​Broad Band HF Terminated 2 Wire Folded Dipole. 

Due to the large amount of common mode noise at my city house block QTH I decided to try a Terminated 2 Wire Folded Dipole to find out if they do reduce the local noise level and how much loss can be expected on transmit. I built one that was 25 metres long with the wires spaced 250 mm apart using some wire and spacers from a previous experiment. The resistive termination was made from 2.7K 4 watt carbon resistors, seven of them mounted in parallel equaling 385 Ohms. A 4:1 balun I had on hand was used just to test the noise level on receive fed by 20 metres of RG-58 Coax. The results were quite a surprise as the local noise level dropped from S5 on a centre fed dipole to an average of almost nothing to S2. A check of the SWR revealed it was less than 3:1 over most of the HF range which was easily handled by the inbuilt tuners in my rigs. This setup was tested for a week using a 10 watt Icom 703+ and found to be effective on 80, 40 & 30 metre amateur bands. As it appeared quieter on recieve and didn't require constant retuning I decided to wind a 6:1 balun to correctly match the 385 ohms balanced antenna to the 50 ohms unbalanced coaxial cable. I followed the IW5EDI design from his web page which uses two tubular ferrite toroids, a 2 turn primary (50 ohm) and a 5 turn secondary (300 ohm) centre tapped to earth. (2.5 turns either side of the earth). This provided a better match all round but more noticably above 10 Mhz. I was quite impressed by the performance of this wide band antenna after having many contacts in the following weeks on 160, 80, 40 & 30 metre bands using my little Icom and 10 watts. The resistors I had used for the termination allowed use of 100 watts PEP so I gave this a go with much further success. I changed the RG-58 coax to RG-213 after it occured to me that RG-58 cable losses may have masked the common mode noise and the SWR but no noticable difference was noted on RX or TX. I was really intrigued by this aertial and felt it was a worth while addition to my mini aerial farm.

My Version of the IW5EDI 6 to 1 Balun

I wound a balun based on the IW5EDI calculations on his webpage. I used two Jaycar type LF-1260 tubular toroids to make my balun. (Pictured with a non-inductive load during testing.)  A multitude of balun ratios are displayed on his page so it's well worth a visit. Of course I made a weather proof case for it from PVC plumbing pipe and fittings complete with stainless steel eyes for support. 

http://www.iw5edi.com/technical-articles/homebrewing-a-balun


Review of Broadcom 3000 Broadband T2FD.

I decided to buy this antenna out of curiosity basically after seeing them on advertised on Ebay Australia for excess of 12 months at what seemed to be an extremely cheap price. It was advertised at AUD$199 including postage from Indonesia to Australia. I thought it would make an interesting comparison against my home brew T2FD with which I had been experimenting. I must say the aerial arrived very quickly, a matter of two weeks via FEDX so that was very pleasing. The construction was heavier and presumably much stronger than my test antenna which looked promising. The main thing was that insulated copper wire was used for the radiator which my modelling had indicated was less lossy than steel.Unfortunately a lot of the extra weight was due to the heavy black poly conduit spacers. The radiator wires were terminated with crimp on eyes that were soldered for reliable connection. The cable ties used to secure the wire to the spreaders and RF insulators were the small black variety which in my experience only last a few years in the sun. The clothes line like cord on each end I replaced as I didn't feel it would last. The termination resistor measured 484 ohms but being sealed I don't know of the construction. The antenna  was quickly installed instead of my shorter home brew T2FD connected up and ready to test. What a shock I received when I switched on my transceiver, the noise level was horrendous, S9 solid, even my HF vertical was quieter at S7.  I have lived in an increasingly, closely populated and very noisey area for 30 years so I am familiar with local noise and HF operation. The new antenna was quickly dropped and replaced with my test T2FD and instantly the local noise was back to S2 inside original device- 3 again so something was not right with my recent purchase. After much thought, and mental diagnosis I decided that an incorrect or faulty RF matching transformer appeared to be the most likely cause/signal path for the local common mode noise to enter the system. At this stage I should have returned the purchase for a refund but curiosity got the better of me again. I simply replaced the RF transformer with a 4:1 balun for a test and re-installed the aerial. The change was dramatic, the noise level dropped to the same levels as the home brew test antenna. Obviously the Broadcom balun or RF transformer had a problem but strangely it still provided a match of under 3:1 so what was happening. To confirm the matching transformer was at fault I  installed an MFJ-915 RF choke on the output from the original matching transformer and the noise level dropped from S-9 to S4-5 which confirmed my diagnosis. Giving into temptation I cracked open the RF matching transformer case and found a tubular winding that appeared to be 9 to 1 ratio but corresponded with the windings of an Unun not a balun. Also one of the connections was bared, twisted, strangely NOT soldered but neverless showed continuity, revealing in my view poor workmanship. I then found that hardware on the inside was only zince plated, not stainless steel, another negative. I again used the IW5EDI balun design and made a 9 to 1 balun which was tekporarily installed into the antenna for testing. An instant difference was noted both in noise level reduction to S2-3 and Testing the Balunalso the match across the HF bandwidth showed 2.5 to 1 and less. I constructed a weather proof plumbing case for this balun with stainless steel fittings inside and out, installed it into the aerial and found the results very pleasing. It has been on test now for a some time now with good reports and stable operation with out incident both at QRP levels and 100 watts PEP. I am still concerned that the black conduit spreaders may contain carbon whic may possibly attempt to absorb some of my RF but in the whole the T2FD design antenna is now behaving very well. I have now had the time to test it over a wide range of propagation conditions on amateur bands from 160 - 6 metres and it has been a pleasant surprize. My situation is far from optimum, the aerial centre is only 30 feet or 10 metres above ground stretching over our house, I mean it has a RESISTOR in the aerial which are commonly associated with losses but they appeared to be minor especially when operating QRP with my IC-703. If I can hear them I can work them which is the crux of the matter. Before this antenna they could hear me but I could only just hear them if I was
lucky or used my MFJ-1026 noise canceller so this design has achieved it's purpose. It may not compair exactly with the performance of a mono-band dipole but it is extremely good and most importantly in my case QUIET.

My verdict is the Broadcom 3000 is a cheap and poor solution. If I didn't have a noise problem initially I would not have realized how poorly constructed this aerial is other than appearance but I venture to say repairs would have been required within 12 months. 

​To those interested in this antennas design I would suggest making ones own version as being the cheapest as it is extremely easy. Buying this cheap antenna was a total waste of money on my behalf and in comparison the construction was basically the same as my very cheap, temporary, homebrew design. If you need to or must buy this design I would recommend buying of the many commercial models available from reputable, well know companies like Yaesu, Opek, Icom, Bushcom, Codan, Barrett, B & W, etc.  I have a preference for copper radiators as I feel they are more efficient but for salt air areas requiring strength stainless steel are an obvious choice. Unless mounted in a high position this antenna is basically an NVIS or near vertical incident which suits me but depending on conditions. However it does reach out rather well to DX as I have found recently which has encouraged me to consider mounting it in a higher position.. 

I will eventually open the 484 ohm termination and report what I find but think there will be zinc plated nuts and washers and who knows if the resistor is non-inductive carbon or what?

More to come.

 

 

 

 


A backup battery pack with solar charging was another project and it charges well in sunny weather. I have since added more high current VR storage batteries to increase the capacity to 290 Amp Hours as I was running out of power! Combined with a voltage and charge level sensitive 230 VAC SLA battery charger for dull weather the system basically supplies most 12 volt DC power requirements within the radio shack. The high current isolation diodes allow the shack to be powered from a normal 240 ac to 13.8 VDC power supply without affecting the battery system or the need for switching.

I have installed a new 20 Amp solar charge controller and a 12 Volt 200 Watt solar panel which is performing very well. I certainly has made a difference to maintaining the charge level of the battery system. The result is that the charger is only required during dull weather which is just what I was hoping to achieve.

 

73 DE Peter

 

 

7372010 Last modified: 2016-06-10 00:23:07, 24038 bytes

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