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Re: Topband: Common mode chokes

To: GEORGE WALLNER <gwallner@the-beach.net>
Subject: Re: Topband: Common mode chokes
From: "Richard (Rick) Karlquist" <richard@karlquist.com>
Date: Tue, 14 Jul 2009 20:42:14 -0700
List-post: <topband@contesting.com">mailto:topband@contesting.com>
GEORGE WALLNER wrote:

> 
> On a separate note, I have been experimenting with twisted 
> pair RX transmission lines. I have used a twsited pair 
> removed from a CAT5 cable. With a well balanced 
> transformer and a common mode chocke at each end, it seems 
> to have very high common mode rejection (i.e. I have not 
> been able to measure it). Loss at 1.8 MHz is about 0.7 dB 
> / 100'. Note that for good common mode performance, the 
> line should be away from other conductors.
> 
> George
> AA7JV

I have used CAT5 pair to make transmitting transformers
at the legal limit up to 7 MHz.  They give you a very
good 100 ohm line for no effort.  I have also used them
for short (30 foot) feedlines for cloud warmer dipoles.
That way, I don't have to have a balun at the center
of the dipole.  I use two pairs in parallel to get 50 ohms.

Rick N6RK
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