[Elecraft] Antenna Theory

[George, W5YR]

Right on, Vic - a case of your writing one thing and my reading another. Our
only point now is that a line with high SWR need not necessarily present any
problems to a balun. It all hinges on the differential-mode impedance at the
point where the balun is connected and, again, high SWR does not always mean
high input impedance which is the most stringent case for a balun. Even a
line with relatively low SWR can have an input impedance at a voltage loop
that can stress a balun.

Interesting stuff, eh?

73, George W5YR
Fairview, TX
w5yr@att.net
http://www.w5yr.com


----- Original Message ----- 
From: "Vic Rosenthal" <vic@rakefet.com>
To: "George, W5YR" <w5yr@att.net>
Cc: "Mike McCoy" <mikemccoy@austin.rr.com>; "Elecraft"
<elecraft@mailman.qth.net>
Sent: Thursday, March 25, 2004 1:16 PM
Subject: Re: [Elecraft] Antenna Theory


> George, W5YR wrote:
>
> > Re 4):
> >
> > Or quite simple if the balanced line is connected to the coax which has,
in
> > my case, five ferrite #43 beads on it, each 1.125" in length.
>
> I was assuming that the open-wire line was being operated at high swr,
> causing the balun to see widely varying impedances on different bands.
>    This would make any balun problematic.
>
> > I have a slight case of heartburn over 2), as well. A feedline may have
a
> > large SWR and as long as the impedance presented at the feedline input
is
> > within the efficient range of the tuner, its loss will be small to
> > negligible.
>
> The 'losses' I referred to were the line losses, not tuner losses.  I
> was comparing a system using coax with one using open-wire line.  I
> assumed that if you are using a tuner, the line must not be flat
> (otherwise, why use a tuner).  Line losses, then will be acceptable with
> the coax system as long as the SWR is moderate.  The open wire line will
> have lower line loss even with high SWR (up to a point, of course).
>
> -- 
> 73,
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco