On 1/23/2013 10:16 AM, N1BUG wrote:
Are you sure, Jim? He said he has carriers every 9 kHz. This is a well
known problem from AM BC mixes in Europe, where their MW BC stations
are spaced 9 kHz apart. I may be wrong but I believe the 9 kHz spacing
is used in the middle east also. What he is experiencing may be the
same issue many us in North America have on 1810, 20, 30, 40, ... due
to mixes or harmonics from our MW BC stations spaced 10 kHz.
Based on his second description (hearing audio modulation on those 9 kHz
spaced signals), I think you're right that they may be coming from some
sort of broadcast intermod. After hearing that second description, I was
hoping someone might have some direct experience with it. In Chicago, I
heard a FEW mixes on 10 kHz increments, the result of a FEW sources, but
not a LOT (the result of MANY sources).
Another clue -- if those are broadcast sources, there will be very
strong carriers that are frequency-stable and quite precisely on 9 kHz
increments (or 10 kHz in North America).
The symptom of EVERY 9 kHz suggests something in his setup may be
strongly non-linear, like a preamp or RX front end that's getting badly
overloaded, or that has poor strong signal performance.
73, Jim K9YC
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