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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.

Jules
g0nzo


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
EA4CYQ
73s
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