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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: "Gary Schafer" <>
Reply-to:, "Tower and HF antenna construction topics." <>
Date: Wed, 31 Mar 2010 17:30:39 -0400
List-post: <">>

> -----Original Message-----
> From: [mailto:towertalk-
>] On Behalf Of Jim Brown
> Sent: Wednesday, March 31, 2010 1:21 PM
> To: Tower and HF antenna construction topics.
> Subject: Re: [TowerTalk] coax stubs /bandpass filter
> 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.
> 73,
> Jim K9YC

As noted in my post; that is why I stated "with a pi network output".

Gary  K4FMX


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