[Elecraft] K3 Multi-Band antenna thoughts

[Robert Tellefsen]

Hi Vic
Yes, I didn't mention it, but there is a 1:1 balun
inside the switch box before the feedline exits on
its way to the rig.

After listening to K9YC at our NCCC meetings, I
think I need to increase the impedance of this 1:1
choke balun though.  It's a bit undersized from his
point of view :-)

73, Bob N6WG

----- Original Message -----
From: "Vic K2VCO" <vic at rakefet.com>
To: "Robert Tellefsen" <n6wg at comcast.net>
Cc: <mike at paxsen.com>; <elecraft at mailman.qth.net>
Sent: Wednesday, March 12, 2008 9:59 AM
Subject: Re: [Elecraft] K3 Multi-Band antenna thoughts


> 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