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OFF TOPIC: Advice on Band Pass/Reject Filter Design




HELP.

I am involved with a 'community radio station' that uses an 847.4MHz
'studio-transmitter link' (STL) that is being catasprophically interfered
with by a paging transmitter combination on 859.8??? (~10W) and 149.??? MHz
(100W). At the worst, the pager was going off every few minutes and
absolutely wipes out our beautiful uplink signal.

We >>thought<< we had no likely overlaod problems. Silly thought!!!


I figure that I need to design and build a receive-only filter unit  - - in
the next few days!!!
Any advice with a filter design will be "gratefully received and faithfully
applied".


The input to the STL is an N-Type connector and I can mount the output of
the filter direct to the STL with the N-Type coax input from the antenna
direct into that. (We now have our Rx antenna about 15 metres above and on
the other side of the self-supporting tripod angle-steel mast from the
pager antennas, rather than in its back-lobe.)

I've considered designs using a set of  helicals in either a die-cast box
or a box made from PCB material.

Is there a filter design program available on the net?


Unknowns:
- The performance of our receiver (info may be available from the
manufacturer.)
- rear/top gain of the pager antenna.


Lessons:
- Only climb a mast alone and at night when you have a death-wish.
- Find out what other services are on a mast before commiting to use it.


Books I have:
- recent ARRL handbooks (1996/7 and 1991 and several earlier)
- 1996 ARRL Antenna Book
- RSGB books of some years ago

As I said, help with a filter design will be "gratefully received and
faithfully applied".

Thanks.

Peter Ellis
VK1KEP
Tech. Adviser - FISH-FM community radio station
Canberra (Capital city of Australia)


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