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Re: [TowerTalk] 160m Shunt Feed

To: "Kelley" <>, <>
Subject: Re: [TowerTalk] 160m Shunt Feed
From: "Gene Smar" <>
Date: Sat, 11 Dec 2010 20:49:01 -0500
List-post: <">>

     The two-capacitor matching system is probably the Omega match.  This 
matching system is typically used on towers that are longer than 1/4 
(electrical) WL.  Most of us mere mortals are confined to feeding shorter 

     If that is the case, you can most likely use a single capacitor of 
appropriate voltage rating as part of a Gamma matching system.  This is a 
single large gauge wire (think CATV coax sheath) or a wire cage of several 
parallel wires supported off the tower by a couple of feet or even more and 
tapped onto the tower somewhere near the top.  The capacitor (usually a 
transmitting variable but can also be a fixed value, once the proper value 
has been obtained) is connected at the bottom of the tower between the end 
of the shunt wire/cage and the center of the coax cable.  The coax shield is 
connected to the tower itself and to the radial system emanating from the 

     Once you have the wire tapped and capacitor connected, you start the 
game of adjusting the cap for minimum SWR, then changing the tap point on 
the tower if you can't get the match low enough.  This may take a few trips 
up and down the tower before you get a decent match.

     You can check out KB9CRY's tower and shunt feed at   .  Mine is pretty similar 
including the wire cage on PVC supports off the tower.

73 de
Gene Smar  AD3F

----- Original Message ----- 
From: "Kelley" <>
To: <>
Sent: Saturday, December 11, 2010 6:57 PM
Subject: [TowerTalk] 160m Shunt Feed

> Multitudes of web pages show, well, multitudes of setups for shunt feeding 
> a tower. Many appear to use a couple of variable capacitors in order to 
> adjust for lowest SWR. Having a limited junk box, what kind of parts 
> should I be looking for to build a generic matching network?
> Thanks,
> Kelley
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