[opendtv] Fox stations disappear ... strange reason

  • From: Doug McDonald <mcdonald@xxxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Wed, 21 Nov 2007 10:47:29 -0600

Last night I could not get any of our three Fox TV stations.

We were having a cold front come in from the west. One station
is 68 mile west, 1 MW, 1300 foot tower. One is 45 miles NW,
1 MW, 800 foot tower, over a small hill. One is 23 miles east,
300 kW, 800 foot tower, over a small hill. All are usually
receivable with small (3-6 dB) signal margin.

I have a permanently installed spectrum analyzer.

Last night the two westerly stations were too weak, apparently due
to the signal being less-than-usually bent down by atmospheric
refraction.

The easterly one was a bit (3 db) higher than normal. BUT ...
about 1.5 MHz below the top of the channel was an interfering
apparently CW signal. It was about 6 dB higher than the ATSC
carrier. I could not tell if it were modulated; even at 30 kHZ BW it
seemed to be pretty much CW, at 3 kHZ it was too noisy to tell.

WTF????? !@$@#$^#^????????????

What is a CW carrier doing at that frequency? This is Ch. 26. There
is a digital station on 25 which is 120 miles east of us and
sometimes comes in, it was in nicely last night, but unreceiveable
because of a co-channel ordinary NTSC.

But the interference on Fox 26 was NOT NTSC! What was it? I worried
about harmonics in my preamp, but the interference was
there with the antenna directly into the spectrum analyzer.

Doug McDonald


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