"Jack Painter" wrote in
news:S%Jhe.6226$It1.5916@lakeread02:

Roger that, thanks for the recommendation Larry. The pager
interference is awful in Hampton Roads, one of the many areas
identified by the Coast Guard as having serious interference to vhf
marine band. The Boston and Cape Cod areas were another area
identified with that problem, I didn't know Charleston was also so
bad. At least part of the problem will be reduced when the new narrow
band radios become prevalent. I can reduce most but not all pager
interference just by setting a receiver to FM Narrow, and this works
even when active splitters, notorious for amplifying pager
interference, are used.

Jack
Va Beach



As long as boaters keep demanding the cheapest piece of crap the
electronics industry can produce....and as long as boat crap discounters
keep ordering $30 VHF transceivers so they can make $100 on each
unit....the problem will never go away.....

Fortunately, paging companies are all going bankrupt from the cellphone
competition...cops are all going to UHF trunk systems...and Motorhola has
bribed the FCC so they won't be selling anyone more VHF business-band
licenses forcing them all to buy into Motorhola's overpriced trunk radio
systems...or Nextel....

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...

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

In article ,
Gary Schafer wrote:

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

I always like the use of 1/4 wave Tuned Stubs for each Paging Frequency
in question. Seems like that always worked for me.....


Bruce in alaska
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