[amsat-bb] Re: Filters and Preamps Question
kq6ea at pacbell.net
Mon Oct 19 17:07:21 PDT 2009
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 at alum.wpi.edu> wrote:
> From: Joe Fitzgerald <jfitzgerald at alum.wpi.edu>
> Subject: [amsat-bb] Re: Filters and Preamps Question
> Cc: amsat-bb at 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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