[amsat-bb] Pre-Amp Help

Zach Metzinger zmetzing at pobox.com
Mon Oct 3 22:26:23 UTC 2016

On 10/03/16 17:10, David Mennerich wrote:
> I recently purchased an Advanced Receiver Research 2M pre-amp to use when
> operating on the LEO SSB satellites.  I purchased the SP144VDG (24 db gain,
> <1 NF).  They don't offer the lower gain, higher noise figure 2M pre-amps
> anymore.
> I tried setting it up this weekend and when the pre-amp is on and I'm
> transmitting on the 70cm band, I'm getting a lot of audio distortion.  When
> I tried this during a pass, my audio on 2M was barely readable because it
> was so distorted, but with the pre-amp off, I sounded fine.

It sounds like the active devices in your 2m LNA is getting crushed by
the output of the 70cm transmitter.

You could try "A Simple Desense Filter for Mode-J Satellites" in
reverse: you want to put the preamp and radio on the 2m side and leave
the 70cm side unconnected.



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