> I always use the 250 Hz 282 filter and I think I want to add a 250Hz
> 9 MHz 219 filter to give me more selectivity.
I have used this combination and it works well within its
limits. The PBT becomes very sensitive and you need to be very
close to the 750 Hz offset in order to hear anything. The other
limit is that the losses from the 219 are about 10 db and the
amp in the front end are not nearly enough to make up for that
(I don't know why, it seems simple to get enough gain in that
stage....) so that when you kick in the NAR filter from 9 MHz,
the signals go way down, and weak ones may be lost. The QRM
does go away though.
I have used an outboard preamp, simple Palomar P-310X to cure
the problem. It interferes with the QSK in a way, but you
can use the preamp with a separate antenna into the other jack in
the back and cure that problem too. I suspect the right way to
handle this is to modify the 9 MHz IF so that you get a little
more gain from the NAR filter there.
Good luck.
Clark
WA3JPG
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