And I've been on the other side of things where the "noise" we had to filter out was so close to the signal we wanted, we had no choice but to put a tight bandpass filter at the antenna, ahead of the amp, to keep the amp from overloading. 6 of one...half a dozen of the other.... 73, jim KQ6EA
--- On Mon, 10/19/09, Joe Fitzgerald jfitzgerald@alum.wpi.edu wrote:
From: Joe Fitzgerald jfitzgerald@alum.wpi.edu Subject: [amsat-bb] Re: Filters and Preamps Question To: Cc: amsat-bb@amsat.org Date: Monday, October 19, 2009, 4:33 PM
what's the preferred order?
As ever "that depends". In the specific case I was involved in at Worcester Polytech, we found that we could get the best trade off by putting the preamp at the antenna then knocking down the out of band stuff with the filter between the preamp and the receiver. The losses in the filter hurt your system noise figure much more if you go ant -> filter -> preamp -> receiver
If the out of band stuff is desensing your preamp, well, that is another story. At +12 dBm for the ARR GaAs FET we were using there was no problem, even in an urban environment.
-Joe KM1P
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