Roy Lewallen wrote in news:V6-
:

Lostgallifreyan wrote:
. . .
Second, I imagined balance to pretty much relate to symmetry. . .

You might find this interesting:
http://eznec.com/Amateur/Articles/Baluns.pdf.

Roy Lewallen, W7EL


Thanks, it is. I read the first part that covered the way RF current can flow
on the outside of a coax, and how the same effect (though as you say, hard to
visualise) occurs in a twin feed line. I see how it applies to the ferrite
'slugs' I shall try once I set something up, though I skipped most of the
stuff on the voltage balun. The current balun made more sense to me right
away.

Note that the idea that has caught my attention is to use transformers..
there would be no direct current contact between either the line and the
antenna, or the line and the receiver. This isn't my own idea, it's just a
wheeze that looks most interesting because it looks like it ought to work,
and if it does it certainly pretects the receiver input rather well. It's
beginning to look as if choosing coax or twin line isn't so important as
knowing if that transformer scheme is valid, so long as I do something to
block common mode currents with a choke balun on the line.