> From: Henry G Chapoton <chapoton@smtp-gw.gdls.com>
> To: towertalk@contesting.com
> Cc: ve6jy@freenet.edmonton.ab.ca
> Subject: [TowerTalk] re: [towertalk] Another Stacking question
To: <towertalk@contesting.com>
> Date: Thursday, July 23, 1998 10:58 AM
>
>
> Odd 1/4 wave multiples force equal currents in the antennas, which
> helps preserve the desired phasing and reduce pattern degradation.
> This is true whether you use 75 ohm for matching or have a 50 ohm
> system with a Stackmatch. A good reference is Llewellen in the ARRL
Hi Henry,
Odd quarter wave lines actually "force" equal currents only at the output
terminals of
the line, not in the element itself. You might not want equal currents in
some
cases, or you might not get equal currents despite using 1/4 wl lines in
some cases.
For example, feeding a bi-square or lazy H, I need equal voltages at each
feedpoint. Gamma matches are somewhere between requiring equal voltage and
equal current in the gamma feed system. (That often messes people up when
they try to phase shunt fed towers with the system Roy uses for series fed
elements.)
It works very well in Roy's examples because the elements are series fed,
and
perfectly symmetrical with respect to the other fed elements, and
symmetrical with the environment
around the elements.
(It also only works when the input terminals see identical voltages, but
that's a cakewalk when the lines are in parallel at the common point.)
It isn't a bad idea, it just isn't the silver bullet it is for applications
other than the system Roy described.
73 Tom
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