Bryan,
No, I
don't have a preamp in the circuit - it would only make things WORSE.
Well, when I add additional cavities it doesn't get rid of the IMD because it's
being generated somewhere else. When I'm not using a cavity the IMD is all
over the VHF band at about -90dBm. However, when the cavity is inline the
IMD is only visible within the passband of the rx cavity. But it's still
there - on channel basically. I can see carriers appear and disappear on
the rx side when the tx is on. I'm thinking that maybe the IMD is being
generated on the tower somewhere. All is the same when I have a bandpass
cavity on the tx side too. Man, the 800 signals are HUGE up
there! All the 800 antennas are the Celwave "Penetrator" antennas.
You know, the ones that are 23ft tall and 8 inches diameter, 12 - 15dB
gain.
Richard
Hello Richard,Have you tried an additional cavity in the rx path? I had a similar situation with a UHF repeater and 800 mhz systems and an additional cavity worked for my problem. Also, do you have a preamp? If so, where in the rx path is it? You should have all the filtering ahead of the preamp.73,Bryan
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