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RE: Topband: Re: Coax capacitor losses

To: "TopBand List" <topband@contesting.com>
Subject: RE: Topband: Re: Coax capacitor losses
From: "Jim Brown" <jim@audiosystemsgroup.com>
Reply-to: Jim Brown <jim@audiosystemsgroup.com>
Date: Sat, 18 Dec 2004 10:30:10 -0600
List-post: <mailto:topband@contesting.com>
On Fri, 17 Dec 2004 20:40:09 -0800, Richard (Rick) Karlquist (N6RK) 
wrote:

>You cannot calculate "loss resistance" using only 
>a Smith chart, and the dB/ft loss specs.

But you had better use a Smith chart for at least part of the design work.  
Based on its length and the frequency at which it was used, at least one 
of the attempts at a coaxial "capacitor" I saw described here was long 
enough that it looks far more like a transmission line than a lumped 
circuit element.  I would be surprised if it's the only one.  That doesn't 
make its use invalid, but it does change the design.

Remember -- once the line is longer than about 1/10 wavelength, 
transmission line effects begin to dominate the behavior of the coax. 


Jim Brown  K9YC


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