Topband: 1.5:1 Bandwidth of shunt fed towers.

[Craig Clark]

K8GG wrote:

>To Broadband a shuntfeed, try paralleling two shunt feed wires.
>I believe Gary Breed, K9AY, wrote something about this a few years ago in
>the Low Band Monitor, edited by Lance Johnson.

Actually, DeMaw did it first in October 1975 QST titled Another Method of 
Shunt feeding your tower He used four wires held together by 4" circuit 
board squares.

The arm is 43" long and the 47' top loaded tower is tapped 26' from the 
base. There is a 1,000 pF cap in series with the feed line. To tune the 
capacative reactance, DeMaw used a top loading wire. I can attest to you 
that a coil at the base is a much easier way to tune the antenna!

I have been using this scheme for years and it gives me a fairly broad 
response across the band. The only difference is I feed my antenna at the 
top in a unipole design.

Another good source of shunt feeding information is the series starting in 
May 1975 Ham Radio Magazine by True.

73 Craig Clark W1JCC

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