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Re: VHF power amplifier with low third harmonic?

I had a problem recently with de-sense.
The VHF TX went through a 5 cavity helical filter (we have big problems with nearby pagers), so I knew it was not a harmonic. It had
to be the main 2mtr signal flattening the 70cms pre-amp.
It was cured by putting a diplexer in the RX path, before the 70cms preamp.

It may be that you need to do this, possibly in addition to filtering the output from the 2mtr amp.


From: =?iso-8859-1?Q?=22Fernandez_Monta=F1a=2C_Juan_Antonio=22?= <jafernandez@iberdrola.es>
Subject: [amsat-bb] VHF power amplifier with low third armonic?

Hi all!

I have tried running some VHF power amplifiers over 100/150 Watios attached
to my TS-790 and all of them gave interference problems to receive the
downlink in UHF.

I even tried connecting a duplexer VHF/UHF in the p.a. output, in the arm of
UHF over a 50 ohmios load, and it reduced a bit the problem but it didn't
desapear completly.

If anybody is running a VHF power amplifier over 100/150 watios and you
don't have problems in your UHF reception, I would apreciate that you send
your experience and tricks to ea4cyq@amsat.org

Thank you very much
Juan Antonio
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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