On Mon, 16 May 2005 09:37:24 -0400, Larry W4CSC
wrote:

Gary Schafer wrote in
:

What size cavity did you say you were using?



It's about 3' long, 8" diam. Don't have any model number on it. I bought
8 at a hamfest for $15 each because it won't work on the 2 meter ham band.
Works great from Ch 10-Ch 72, about as far afield as we get....

Your cavities must be new to have such wonderful specs...(c; You could
parallel those and offset the tuning on each to cover a wider bandwidth, I
suppose....Maybe parallel two, one for Ch 6-22A and one for 68-72? Two
humps in bandpass...

The 8" is not quite as sharp as the 10". The 8" at .5 db insertion
loss shows: at 1 mhz away it is down about 15 db. At .5 mhz it is down
about 8 db.
At 5 mhz away it should give abut 30 db attenuation. That should wipe
out the paging transmitters but the pass band is still too narrow to
cover much of the marine band. Fine for a single frequency.

Like you say, if you had two of them in series and stagger tuned them
then you would probably be ok. You could get an adequate bandpass for
most of the marine channels. Although the insertion loss would be a
little higher. The rejection at the paging frequencies would be
greater too.

Regards
Gary