[Elecraft] Balanced solution for KAT500 tuner?

[Jim Brown]

On 9/29/2012 5:40 AM, Barry, Stephen wrote:
> Does Elecraft have a balun solution for balanced feeders for the KAT500 at 500 watts?

See the Choke Cookbook that is Chapter 8 in my RFI Tutorial, and the 
discussion in the preceding pages, for an excellent common mode choke 
that will satisfy this need.  Use one of the chokes that is bifilar 
wound with #12 THHN, connected as a parallel wire transmission line 
between your parallel wire line and the tuner.

http://audiosystemsgroup.com/RFI-Ham.pdf

BTW -- the words "balanced feeders" and "balanced feedline" are pure 
fiction. You will note that I used the words "parallel wire" to describe 
the feedline.

The balance of any system, including an antenna system, is defined equal 
impedances to the reference plane. For antenna systems not on aircraft, 
that reference plane is the earth, and the transmission line is only 
part of that system. Most wire antennas that hams are able to erect are 
unbalanced by their surroundings, which in turn causes the feedline to 
be unbalanced. Imbalance in an antenna is caused by off-center feed, 
ground slope, sloping wires, trees, buildings, even the varying ground 
conductivity around the antenna.

This imbalance will cause current on the feedline to become unbalanced, 
which makes it part of the antenna. The feedline picks up noise and 
couples it to the antenna (because it's part of the antenna).

For this reason alone, smart hams have learned to use a common mode 
choke at the feedpoint of an antenna  This decouples the feedline from 
the antenna, preventing noise pickup (and keeping RF out of the shack).

73, Jim K9YC