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Re: [Amps] low pass filter fail

To: 'Jim Thomson' <>, 'Ian White' <>,, 'Benedikt Sveinsson' <>
Subject: Re: [Amps] low pass filter fail
From: peter chadwick <>
Date: Tue, 29 Apr 2014 17:32:23 +0200
List-post: <">>
I don't know how much harmonic attenuation you would get in the matching 
network for a solid state 2m PA, but at 500 watts output, it might not be as 
much as 30dB, and then you need 40dB from the stubs. So a low pass filter has 
its attractions, if only as an additional filtering stage. A valve PA, on the 
other hand, is likely to start from a better position in that the harmonics 
will be attenuated by the relatively high Q tank circuit.

One has to consider what variety of LPF, too - Butterworth, Tchebycheff or 
Cauer-Tchebycheff, although that last one might be a bit impractical at these 
frequencies. The variety also affects the cut-off frequency definition.


Peter G3RZP
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