Re: Eliminating Desensing
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@hrblock.com Sent: Jun 30, 2008 12:50 PM To: amsat-bb@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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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. 73,
...hasan, N0AN
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@hrblock.com Sent: Jun 30, 2008 12:50 PM To: amsat-bb@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.
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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participants (2)
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Andrew Glasbrenner -
hasan schiers