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Author Topic: station filtering among ham bands...  (Read 669 times)
EI4HQ
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Posts: 50


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« on: July 25, 2003, 03:07:04 AM »

Hi,

I operate a 25w beacon on 28.209MHz (EI0TEN). Unfortunately, I've recently had to relocate the beacon to my home qth and here it'll remain for the foreseeable. Consequently my ability to operate on 10m (and to a lesser extent 12, 15, 17 and 20m) is significantly compromised.

Any suggestions for how I can best filter out the 28.209MHz transmissions in the rest of my station? I've looked at Dunstar filters etc. which are fine for the bands other than 10m. What can I do about 10m however? Is a very narrrow bandstop filter a possibility (i.e. built to stop 28.209MHz)?

Any advice and/or suggestions appreciated.

Cormac, EI4HQ
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WB2WIK
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Posts: 20611




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« Reply #1 on: July 28, 2003, 03:10:00 PM »

Sure a good bandstop filter in your 28 MHz receiver should help a great deal, provided the beacon transmitter is clean and not generating wideband noise.  A crystal-controlled linear transmitter (not frequency synthesized) can be made to be extremely clean, with virtually no single sideband phase noise.

Obviously, keeping the beacon transmitter power to the lowest level possible will help a great deal in minimizing interference to the rest of your station; as will antenna separation!  When I've run beacons, or even VHF repeaters, from my home stations, I've always had a great deal of separation between beacon/repeater antennas and my main station antennas, in an attempt to minimize interference and desensitization -- and this works very well.  Using a vertically polarized 10m beacon antenna (which will work just fine for ionospheric propagation) and a horizontally polarized beam antenna for general 10m operations, and placing the beacon antenna at a beam heading that you'd rarely use to work anybody, can provide you with another 20 dB of interference rejection, even on a fairly small lot.

WB2WIK/6
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