At 5/5/2004 08:56 AM, you wrote:
>I've seen some of the other posts. You should be running
>a dual port circulator in addition to the proper duplexer.
As Richard has correctly indicated in his previous posts, an isolator will
not have an effect on his IMD problem.
Having said that, however, it still would be a good idea to put a
single-port isolator on the TX. The reason is so that the RFPA "sees" 50
ohms over a broad bandwidth. Some RFPAs (like the high-power GEs) don't
like to see pure reactance anywhere within their operating range, even if
it's not on the frequency where power is being generated.
My guess is that the IMD is in fact being generated on the tower. 95% of
the on-site mixes I discover these days are found in tower joints,
electrical conduit, air conditioning ducts, etc. One just popped up on my
input after changing a 420 link channel (2 watt TX 100 ft. below main RX
antenna). I didn't even bother to look for the sources; I just decided to
swap link channels again.
Bob NO6B
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