Tom -
Living near six AM stations, I can sympathize :-)
Step 0 - turn off the noise blanker, any DSP, auto tuner, etc. Get down
to the naked receiver. Junk still there? Proceed...
If you switch in the attenuator on the receiver, does the junk drop by the
same amount as the attenuation or more? If more, or if it goes away, you
are suffering from front-end overload. The cure is to get a BC-reject
filter and put it in the receiver antenna path, which is a problem for the
TS-850 as it has no external receiver loop. (There are modifications to
do this - fairly easy, too...and quite useful.) Check out ICE or Kiwa
Electronics.
If it's not overload, then something nearby is acting as a mixer.
Anything that looks like a diode to RF will produce exactly the symptoms
you are describing. Have you added any equipment to your station that has
a long-ish cable attached? I had an similar problem with a Tailtwister
control box that has several un-bypassed diodes inside - the long rotor
cable conducted strong BC right into the diodes and then was perfectly
happy to re-radiate all of the mixing products. This type of mixing will
happen whether the equipment is on or not. Try disconnecting all of your
equipment from the feed/control cables one cable at a time and see if you
can isolate the guilty party.
If you get to this point, you have a bad connection somewhere in your
system. Clean any bulkhead connectors, check for cold solder joints in
the tuner, at the feedpoint, on any other antennas. It could be anywhere.
Look on the bright side - by doing all this, you're performing excellent
station maintenance :-)
Good hunting!!
73, Ward N0AX
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