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Re: [TowerTalk] Ferrite Balun on a LPDA?

To: <>
Subject: Re: [TowerTalk] Ferrite Balun on a LPDA?
From: "Mark Beckwith" <>
Date: Fri, 15 Jun 2007 04:51:28 -0500
List-post: <>
Tom, how would you recommend feeding/decoupling the feedline on a Tennadyne 

Mark, N5OT

> Arne,
> The Tennadyne log has two hot booms. Each boom is used as a
> conductor in a balanced transmission line. The elements are
> attached to those transmission line conductors which also
> serve as a boom.
> Many people install the antenna by placing a balun out at
> the end of the booms. This divorces the boom to coax shield
> path.
> Then they run the same coax they decoupled right along the
> boom, often taping it right to the lower boom.
> Now they have the coax shield they painstakingly decoupled
> from the boom being tightly coupled to a hot boom! The
> mutual coupling is so high it undoes what the balun did, and
> they are back to square one with terrible common mode on the
> coax. It's just about as bad as using a balun at the
> feedpoint of a dipole and then taping the coax to one leg of
> the dipole for 15 feet after the balun.
> None of this applies to any other system, unless that system
> has a "hot boom".
> 73 Tom 


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