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[TowerTalk] Re: Loading C31XR boom for 80m

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Subject: [TowerTalk] Re: Loading C31XR boom for 80m
From: (
Date: Fri, 25 Jan 2002 07:08:40 -0600
The wire loaded boom extensions is a good idea, electrically.
Mechanically, there is the huge problem of keeping the wires
from getting blown around guy wires and / or the tower and beam.

The sidemounted beam in the middle of the tower may or may not
be a problem, even on 160.

I had a 130 ft ft tower with a 3L15 on top (20M beam never got installed)
plus an 80M inverted vee at 100 ft shunt fed on 160M where it was a
very competitive antenna.

When I side mounted a 3L20 at 62 ft, the SWR on the 80M inverted
vee went up considerably.  I assume there was an 80M resonance 
between the 3L15 on top, 70 ft down the tower, to the 3L20 at 62 ft.

The shunt fed tower still worked on 160 but no longer felt as
competitive.  I did not model it, but I'm guessing the lower beam
effectively lengthened the tower enough to cause a current reversal
with subsequent cancellation of low angle radiation.  Modeling the
system on EZNEC should tell whether the side mount will help or
hinder operation of the system on 160M.

For 80M, sloping dipoles or sideways mounted V's ( < > ) may be
an effective option.

Tom  N4KG

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