John Lloyd wrote:
>
> Several years ago, I had a similar problem with AM stations 1510 and 910
> that were 600 khz apart. They were both about 5 miles away from our
> repeater. Our 146.94 repeater when it keyed up was hearing the audio
> combination of both AM transmitters that were on during the day. The
> problem went away at sundown when the one AM station went off the air
> and returned the next morning at sunrise when it came back on.
>
> We traced the IMD mix point to a guy wire anchor plate on a nearby 120
> ft tower that was rusty and it wasn't even galvanized! We solved the
> problem by adding wire jumpers with cable clamps from each guy wire to
> the anchor rod which shorted out the diode action of the rusty anchor
> plate.
>
> John, K7JL
John:
We had a very similar problem in the Washington, D.C. area with our
147.00/146.40 repeater, however it was a 160 Meter dipole off the 200
foot self supporting tower about 30 to 40 feet from the duplexed
repeater antenna.
We raised and lowered the dipole for experimentation purposes while all
were listening to duplicate the problem. All listening appreciated the
education from it. You could hear the stronger of the two AM stations
come and go as we raised and lowered the dipole.
We went to remote receive sites instead of a duplexed repeater and never
looked back!
Tony, K3WX
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