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Re: [TowerTalk] coax stubs /bandpass filter

To: "Tower and HF antenna construction topics." <>
Subject: Re: [TowerTalk] coax stubs /bandpass filter
From: "Jim Brown" <>
Reply-to: "Tower and HF antenna construction topics." <>
Date: Wed, 31 Mar 2010 10:21:26 -0700
List-post: <">>
On Wed, 31 Mar 2010 10:17:13 -0400, Gary Schafer wrote:

>It is not resonant at the
>harmonic frequency and acts just as a low pass filter with a low source
>impedance at the output of the amp at the harmonic frequency.

As noted in my tutorial, that's true for some amps, but not for others. For 
MANY amps, the last output filter element is a series inductor, making it a 
relatively high impedance at the harmonic.  For such an amp, the best place 
for the stub is very close to the amp. The tutorial includes a matrix listing 
many popular amps, thanks in part to feedback received when I asked about 
amps on this reflector several months ago. 


Jim K9YC


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