[Elecraft] Slightly Unbalanced dipole?

[Al Lorona]

You guys keep talking about coax-fed antennas. Yes, although it may be easy to wind coax around a toroid and put it up at the antenna midpoint, that's not so easy with open-wire line. This discussion was very coax-centric and I wanted to open your minds that not everybody feeds their antenna with coax.

Balanced feedlines ("window line" or "open-wire" line) can have significant common-mode current. They're not immune to the effect. (I know you know this; I'm saying it for the benefit of all.) A device with high common-mode impedance, located right at the output of the tuner, suppresses common-mode current on a (balanced) feedline. That's it's purpose.

I'm in agreement with you about the 1/ cause of common-mode current and the 2/ cure for it. I'm simply saying that for convenience's sake, consider putting the choke at the tuner output.

A choke with high Z to common-mode current, external to the tuner, in a non-conductive box, with as short a connection to the tuner as possible, does quite well at suppressing common-mode current. I'll be happy to share my measurements with you. 

There is no coax anywhere in my antenna system. So my solution was to put a choke with high impedance to common-mode current right at the output of my antenna tuner. I encourage users of open-wire line to do that.

Al  W6LX

>>> In all cases of a radiator fed with coax,