> From: Peter Chadwick <Peter.Chadwick@gpsemi.com>
> To: amps <email@example.com>
> Subject: [AMPS] neutralising
> Date: Fri, 20 Jun 97 13:32:00 +0000
> >That's why I am not enamored with tunable PA's that have RF
> >feedback from the output to the input in an attempt to decrease
> >distortion. For every tuning condition where distortion is reduced,
> >there is one where distortion is enhanced.
> Interesting comment. I'm not totally sure that companies like Marconi,
> Collins, Racal etc would agree. On the other hand, I may be trying to
> apply your comment to auto tuned professional amplifiers running into
> <2:1 SWR all the time, when you intend the comment to apply to ham radio
> linears, which are a totally different situation.
Right Pete. Phase shifts with tuning, Unless there is some way to
guarantee the user ALWAYS sets the tank and input circuits to the same
resonant point where feedback was optimized , negative feedback can
become more positive.
For the general population, less feedback is better. Also the modern
exciter is so dirty, a conventional GG triode adds insignificant IMD
to the system.
73, Tom W8JI
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