Hi Tom

I use a Q section of 100 ohm "coax" (2x 50r cables side by side with
shields joined at each end) on my 20m single loop quad (about 140 ohms
modeled) I went for the higher load Z (200r) because I wanted a higher
SWR b/w and the possibility that it might work on odd multiples (not
that there is an amateur band on 42MHz! - Thinking about a 30m version)

It seems to work well but it isnt as if I have made any serious
comparisons. Its 2:1 SWR b/w is something between about 13.5 and 15MHz.

All you need is coax and allowance for velocity factor!

Dont know about the balance/unbalance side of things so much. I was
getting some shack radiation that a choke balun (turns of coax on an air
core) where the feed met the Q didnt seem to help much. The antenna
itself is only 8-10m from the shack anyway.

I can send you the modeled details if you like.

Cheers Bob VK2YQA

Tom Coates wrote:
I'm seeking a 4:1 balun design that could handle 10 watts efficiently on
20M and would be easy to reproduce without purchasing special ferrite cores,
etc.