You guys were very helpful with our last co-location problem (147.225-
and 146.925+), now I have another.
Now another gentleman put up a machine on 224.340/222.740 near a
machine on 443.550/448.550. When 220 comes up, it keys the 440
machine. When 440 comes up it desenses the 220.
Both have Stationmasters on the same tower and the antennas overlap
about 2 feet (440 is above 220). I believe both are using BpBr
duplexors. 220 is running around a 90 watt amplifier. 440 is at
about 20 watts. 220 has a preamp with some sort of filter in front
of it. 220 is a Hamtronics, and 440 is a Kendecomm. I know the
solution could involve switching to Moto/GE but before they do that,
what can be done first to work with what is available?
I bench tested the 220 rx at .15uv for 12db sinad without the
preamp. So I told the guy to first ditch the preamp and see if that
helps his desense on 220.
I thought a bandpass on each machine might help but I don't know what
effect it would have on what I suspect is the culprit, the harmonic
of 224.34 which is 448.68...very close to 448.55 the input on 440.
Also, Tx/Rx says they don't make a 220 bandpass.
Moving the 220 antenna down 10 feet might do the trick also, but I
think this guy wants to keep all the height he can since this is only
a 75ft tower to begin with and he is side mounted at about 60.
BTW, this hill has 2 VHF, 2 220 and 2 440 machines on two towers. I
suspect that makes it a prime location for some commercial (Moto/GE)
equipment, but my Hamtronics station is doing fine, for now, and I am
just trying to help my neighbors with their problems.
PS. You guys make me look good! Thanks for all the "lessons".
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