[amsat-bb] Re: Eliminating Desensing
schiers at netins.net
Tue Jul 1 16:14:52 PDT 2008
Good diplexers are an excellent solution, Drew. I use them here, and all
problems were eliminated. I put them in front of the preamp (somewhat
compromising the NF), and have found that the NF and gain are still
quite adequate to get the best performance on the birds.
Andrew Glasbrenner wrote:
> It's unusual to see desense on 2m receive from a 70cm uplink, but I think the same solution can be applied. Many use a common 2m/70cm diplexer as a high pass/low pass filter. In this case you would want to feed the 2m antenna to the common port of the diplexer, and the 2m port of the diplexer to the input of either your preamp or rig if you do not have a preamp. This blocks your transmitted signal from the receiver/preamp input very effectively. http://www.amsat.org/amsat-new/articles/Mode-J/ describes this for 70cm desense issues.
> Another option is to use a preamp with good filtering on the input. I had issues with Mode J desense with my Icom AG-35 preamp, but have none now that I have switched to SSB Electronics preamps.
> As always, Your Mileage May Vary (YMMV).
> 73, Drew KO4MA
> -----Original Message-----
>> From: "Reicher, James" <JReicher at hrblock.com>
>> Sent: Jun 30, 2008 12:50 PM
>> To: amsat-bb at amsat.org
>> Subject: [amsat-bb] Eliminating Desensing
>> I got significant de-sensing of my 2 meter downlink from my 70cm uplink at Field Day. I know a good part of it was due to the short cross-boom (about 4 feet) I was using. I would like to decrease the de-sense on this set-up before I permanently install it at my home station. Any and all suggestions are welcome.
>> 73 de W0HV, Jim in Raymore, MO
>> Light travels faster than sound... This is why some people appear bright until you hear them speak.
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