[TowerTalk] Fwd: Fwd: effect of two wire antennas end to end

[Jim Brown]

On Wed,2/25/2015 4:30 PM, Hans Hammarquist via TowerTalk wrote:
> if you try to put a common mode choke at the antenna I can imagine difficulties with overheating etc as the voltage is high.

Huh? A proper common mode choke can handle legal limit at the feedpoint 
of centerfed dipole fed with coax. Study k9yc.com/RFI-Ham.pdf

> I allow the unbalance current through the feeder and I stop it after the tuner.

That setup WILL have interaction between feedlines, and the feedlines 
will pick up RF noise that they will couple to the antenna.

> A well design (unlike mine) Windom, or Off-Center-Fed antenna has a resistive 200 - 400 ohm impedance at the feeding point allowing for a balun at the feeding point and a reasonable SWR in a coax feeder. I will not recommend what type of balun to use but imagine that the "right' balun reduces any common mode current outside the coax.

There's  FAR too much imagination (as in Alice in Wonderland) in that 
paragraph.  The word "balun" is far too vague, because it is used as if 
it were some magic box that solves all problems, and has no 
limitations.  I believe in calling a spade a spade. An ordinary 
transformer, wound on a low loss ferrite toroid, and with sufficient 
insulation between the windings and the core, could isolate the line 
from the antenna, thus reducing the common mode current.  That 
transformer will kill common mode current on the feedline ONLY if it is 
at the antenna.

> I have not problem with overheating maybe my 100 W is one reason.

It certainly is. Try running an amp.

73, Jim K9YC