Roy Lewallen wrote in message ...

No. A "non-radiating" feedline is one which has no significant amount of
common mode current. This can be accomplished by making the feedline a
length such that the induced current is minimal; by inserting a balun or
baluns; and/or by placing the feedline symmetrically with respect to the
antenna. I thought I had explained this -- I don't seem to be
communicating well.



What's up Roy? Long time no see!

Ok, well, I'd like to discuss this a bit.

So for most of the dipole based antennas (including Yagis), you
can use 6 turns of 4" diameter coils in the coax, to make an inductive
loop that is supposed to prevent current from moving down the outer
braid (non-radiating).




We've been down this path before, and you've shown that you won't accept
the fact that SWR has nothing to do with whether or not common mode
current exists on a feedline, and there's nothing I've been able to do
to convince you otherwise. You also either haven't read or won't believe
that it's common mode, not differential, current that causes a line to
radiate and thereby contribute to the overall pattern. But hopefully
other readers have learned from this exchange. Once the basic principles
are grasped, these phenomena lose their mystery, and they're no longer
"unpredictable", but readily measured, modeled, and understood.


Ok, so I understand how the common-mode-rejection-ratio works with
an audio amplifier that has an XLR cable input: signals in phase
(common
mode) will cancel each other out when they reach the input transformer
(balun). And although the XLR cable is shielded, the two signal wires
are more like a twin-lead transmission line instead of like coaxial
cable.

So i'm not sure how to ask this, but coxial cable is obviously a
much different beast than twin lead, so the concept of common-mode
currents
radiating from the line is a bit strange because the outer braid
completely
encloses the inner radial. But this is weird because coaxial cable is
unbalanced already, while twin-lead (or in the case of the audio XLR,
shielded twin lead) is balanced.

This is a discussion he

http://lists.contesting.com/archives.../msg00484.html



Slick