Dummy wrote:
"One wide-band antenna was hooked up on a spectrum analyzer."

Years ago, from time to time, I`d hear the sheriff`s dispatcher in the
background, and sometimes TV Channel 8 audio, when monitoring a certain
2-meter amateur repeater. It stopped when the Sheriff changed
frequencies.

Turns out the difference between the sheriff and Channel 8 frequencies
matched the IF of my Icom radio. When the repeater opened my squelch,
there the other signals were.

In 1949 I used to turn on the Mighty 790 here before 5:00 a.m. when we
signed on back then.

From my monitor loudspeaker I could hear KTRH, the 50 KW station about
15 miles away which was already broadcasting. The tiny 740 KHz signal
was mixing with the carrier in my final and being rebroadcast. Now both
stations are owned by Clear Channel so it would make no difference. It
made no difference then either because the 740 KHz signal on the 790 KHz
signal was more than 50 dB down. That`s under the FCC requirement at the
time.

I think the spectrum analyzer antenna is clean and the "spur" is a
simple mixing product.

Best regards, Richard Harrison, KB5WZi