Topband: Dual band shunt-feeding tower on 160/80

[Gene Smar]

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 at n1bug.com>
To: "Gene Smar" <ersmar at verizon.net>
Cc: <topband at 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
>