Paul:
My tower is a 64-foot tall Tryon self-supporter - shorter than yours.
Top loading is provided by a Bencher Skyhawk ten-element triband Yagi where
I shorted the parasitic elements to the boom with aluminum straps. I'm
speculating here that the size and loading configuration of each tower will
result in a better or worse performing shunt feed or sloper wire. I got
lucky that nearby trees and the arrangement of the aluminum and steel of and
around my tower conspired to allow my shunt-feed and sloper to work for me.
YMMV.
73 de
Gene Smar AD3F
----- Original Message -----
From: "N1BUG" <paul@n1bug.com>
To: "Gene Smar" <ersmar@verizon.net>
Cc: <topband@contesting.com>
Sent: Monday, August 26, 2013 12:49 PM
Subject: Re: Topband: Dual band shunt-feeding tower on 160/80
I've done exactly what Herb suggested: hung a sloper for 80M off the
side of my 160M shunt-fed tower. Neither antenna knows the other is
there
and both work pretty well - meaning I'm satisfied with what I get out of
them.
Interesting. I have tried verticals, slopers, inverted V's and other 80
meter antennas on or near my 160 meter tower with little success. The
impedance of any such antenna seems to be severely altered by the nearby
tower. I suspect it depends on the electrical length of the tower. Mine is
close to an electrical half wave on 80 - 100 feet of Rohn 25 with a 7
element 6 meter yagi, approximately 30 foot boom sitting at 103 feet.
At one point in time the 160 meter shunt feed could be made to provide an
excellent match on 80 simply by changing the series capacitance. However,
after I cut down several nearby trees that no longer works.
73,
Paul N1BUG
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Topband Reflector
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