End Fed Random Wire Antenna for HF

 After my successful build of the BBTD antenna, I started to wonder if the terminator resistor was actually needed, and if perhaps using a matching transformer would allow a lot of latitude when designing other antennas. I started to experiment and researched other antennas, in particular the Rybakov 806 design. This antenna is based on a length of wire (7.6m) that, as far as I know, is not resonant on any of the desired frequencies and is erected vertically using a matching transformer at the base. The Rybakov needs radials to perform well.

I do not profess to know exactly what or why I am doing these experiments, but that's exactly what they are to me - experiments!

My experiments used the 9:1 matching auto-transformer of the KISS Balun type. It is technically not a balun but an impedance matching auto-transformer. The transformer can be constructed using two ferrite beads large enough to pass the wire windings through. I used 1.5mm stranded wire so the holes need to be about 6 to 8mm diameter. Bind the two ferrite beads together with tape and/or cable ties to form a 'binocular' style ferrite. A better solution for the core would probably be a FT240-43 toroid and wound accordingly for a 9:1 ratio. I attached a completely random length of wire which meanders all over the place through the garden on the fence (approx 140 feet long) which is horizontal for most of its length. The ground connection was made via approximately 33 feet of wire (later shortened to about 8 feet) connected to a cold water feed pipe. Although using this method of grounding is frowned upon, it was the most convenient earth at the time. Please don't use this grounding method as a long term solution as you could get stray currents flowing into your household appliances and RFI problems. I didn't think for a minute that it would work with any usefulness, but you know, you have to get these ideas out of your head! The SWR readings can be seen below:

1.8MHz - >10:1 (useless)

3.5MHz - 3:1 (ATU)

7.0MHz - 1.3:1

10.1MHz - 1.4:1

14MHz - 1:1

18.07MHz - 1.8:1 (ATU)

21.0MHz - 1:1

24.9MHz - 1.1:1

28.0MHz - 1.6:1

50.0MHz - 1:1

So the SWR readings are not all that bad. As we all know that's not the full story. The length of the radiating wire doesn't seem critical, but as long as possible is best. If it can be laid out in a straight line and also as high as possible, this also helps, but is also not critical to the SWR. But does it perform? Yes and no. I can make contacts on it all over the place, again on FT8. I can't seem to make any voice contacts at the moment, no matter which antenna I use. Listening to most of the SSB conversations though they are all mainly using very high power and multi element beam antennas compared to my menial 10 Watts on a homebrew! Some of them are on anything from 400 to 1000 Watts. I can't compete with that!

One conclusion I have come to, after making some comparisons, is that these wire antennas with matching transformers are a 'Jack of All Trades but Master of None'. They cannot perform as well as a proper tuned antenna for a specific band, for example the 14MHz 'Inverted V' I have on my gable wall, but they do get the job done for people with limited space and resources. If the antennas were installed at a decent height above ground I'm sure the performance would improve dramatically, but I have no provision for that here. On to the next project which will be another antenna - vertical this time. I understand that verticals tend to give you a better 'take-off' angle for DX when propagation allows. It will be a shortened antenna because I can't have a 60 foot monstrosity in my garden! 

(Update - I tried the antenna with a 16:1 transformer but made it with isolation between primary and secondary. I then shortened the radiating wire length by about 8 feet. Arguably it is working a bit better than before. The SWR hasn't changed much, if anything it has improved.)