[Elecraft] KPA500 RF output wiring

[Jim Brown]

On 9/10/2011 11:05 PM, Gary Hinson wrote:
>> Sure. Twisted pair is a VERY effective transmission line, and that is
>> what is needed ...
> Hey Jim, what kind of twisted pair could I use to feed my [mostly 50 ohm] HF
> antennas?  Coax is expensive in ZL so I'm willing to try alternatives.  I'm
> even thinking of homebrew balanced line with baluns at the bottom (a
> coax-fed remote antenna switch in my case).

Coax is expensive in the US too :)  The key to loss is conductor size 
and impedance. The parallel wire cable sold  for use with loudspeakers 
would make decent parallel wire antenna line. Twisting has the advantage 
of greatly reducing crosstalk and radiation/pickup to/from the line.  
RG8 uses #14-#10 for the center conductor, most copper braid shields are 
equivalent to #10 at DC and a much larger conductor on the higher HF 
bands (thanks to skin effect).

#12 parallel wires or twisted pair would probably be equivalent in loss 
to very good RG8, and in the 50-70 ohm range for impedance.  At HF, 
dielectric loss doesn't matter, but the dielectric will affect Vf.

You will need common mode chokes at both ends -- remember, most real 
world ham antennas are unbalanced by their surroundings.  It's a mistake 
to call cable like this a balanced line. It's a parallel wire line or 
twisted pair line.

73, Jim K9YC