[Elecraft] K3 Multi-Band antenna thoughts

[Vic K2VCO]

Robert Tellefsen wrote:

> To make antenna matching easier for the TX, I have a
> homebrew relay box that adds in various lengths of more
> 450 ohm window line to bring the feedpoint reactance
> down to close to zero.  This gives the ATU a chance to
> match easily and gives the best 2:1 swr bandwidth.  The
> single band antennas are coax fed, but still switched
> through the relay box.

I do something similar, although I use inductors and capacitors rather 
than pieces of line. This is very important to make a balun connected 
between the balanced line and the coax efficient. I conducted a series 
of tests in which I measured the temperature rise in the balun -- a sure 
indicator of losses -- when the mismatch was primarily resistive or 
reactive. Reactance is poison for balun efficiency!

And yes, you need a balun to reduce noise pickup, line radiation, and 
rf-in-the-shack.
-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco