[ARC5] ARC-5 Unun Match

[J Mcvey]

I mentioned my ARC-5 matching unun a few posts ago .It was only a 1:4 and I decided to give it more flexibility by making it a switchable 1:4/1:9 .
The original unun at the top was a bifiler wound torroid which I simply added another 10 turns of #14 THHN on it.Then I decided to make a new one with tri-filer windings.
Ironically, they both performed about the same in the 40 to 80 meter range.I used the tri-filer wound one in the final assembly in the picture.
Both ununs had some leakage inductance up to 50 ohms of reactance at 7.3 MHz.
To counteract this and to make the rollers useful as antenna tuners, I added two paralleled 100pf (200pf) transmit caps  in series with the tx antenna input on the antenna switch. The rollers tune at the low end of their range with this configuration . With the reactance low, the component stress is kept  to a minimum.Both transmitters push out 45 watts  CW. IF I tweak things the right way, I can get over 50 watts, but that's more than the ARC spec sheet says, so I don't run it  that way.

All of this was constructed with a re-purposed box, and a T-130-2 core I paid $1 for at a Ham fest. ($5 on Ebay)The magnet wire was #16 heavy insulation.The MyAntennas.com site wants $130 for a dual match unun - and it doesn't even have a switch!


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