Hi Marv,
Dan K6MHE wrote an article showing how he drove a 33' radiator on 40m and 20m
w/o any switching (and no traps). The network uses one variable inductor and
two variable capacitors. See http://www.k6mhe.com/opuscules.html for details.
In fact, AB8XX adapted it to work on 80/40 (see his YouTube video clip:
http://www.youtube.com/watch?v=WMfI_WRAIYQ). W7ZOI is credited with the concept.
vy 73,Bryan WA7PRC
Date: Fri, 18 Mar 2016 09:26:54 -0700
From: Marv Shelton <marvs@att.net>
To: towertalk@contesting.com
Subject: [TowerTalk] 40/80 meter vertical
It seems like it could be done. You will need the right-sized aluminum pieces
for the lower section and something for the upper, which I would think you
could also do with wire. To calculate the distance to the 40 meter trap, you
could model it in EZNEC if you can get the electrical specs on the trap itself.
Come to think of it, its probably a good idea to model the basic antenna and
your 40/80 version to see what advantage if any, you get from removing the
traps for the other bands. Some might argue its not worth the trouble, and if
it ain't broke, don't fix it.
Marv wa2bfw
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