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Hetrodyne on WBBM 780 near sunset 8/18

T

tvnut

Driving through central Indiana yesterday in the late afternoon and early evening, I tuned to WBBM 780 for an update on storm coverage on my quite sensitive AM car radio. That I received, along with a nasty heterodyne. Even someone who knew nothing about radio signals would say, "What's that whine?" It was only on WBBM. Couldn't get anything on 770 or 790, which leads me to believe it was another North American 780 off frequency. Europe is 783 so Iran or Saudi Arabia on a night path isn't likely.

Ideas?
 
I wonder if WBBM was running (testing) their new Des Plaines transmitter tower and also transmitting from their licensed tower in Bloomingdale at the same time. Perhaps that could produce the heterodyne you were hearing. I drive past Des Plaines site quite often, and I have noticed that there is work being done on the NW tower.
 
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CADXER said:
I wonder if WBBM was running (testing) their new Des Plaines transmitter tower and also transmitting from their licensed tower in Bloomingdale at the same time. Perhaps that could produce the heterodyne you were hearing. I drive past Des Plaines site quite often, and I have noticed that there is work being done on the NW tower.
Click to expand...
I wonder too. The licensed at 780.0 and the test tuned a bit off, at 780.05 or .1? And in the process of being manually tuned to match? Interesting notion. If I was WBBM, I'd be doing that at 1 a.m. against a frequency measurement receiver, not making afternoon drive a howlfest.
 
Tuning the antenna will have zero effect on the frequency. None. Impossible.
Adjacent station with a spurious signal in their sideband.
Your cars electronics.
A phone charger.
But not WBBM.
 
@ TV Nut:

I'm presuming the whine was not a lone, solid tone ; more of a mix of tones -- a buzz. You being live to DX would be able to tell if it was a genuine het.
The time of day you mention did mean that path of darkness existed east for about 12,000 miles :) , so ......

How about an off-frequency Cuban? True, that island is way south of you, but it still would be nighttime there.....
 
Steve Green NEPA said:
@ TV Nut:

I'm presuming the whine was not a lone, solid tone ; more of a mix of tones -- a buzz. You being live to DX would be able to tell if it was a genuine het.
The time of day you mention did mean that path of darkness existed east for about 12,000 miles :) , so ......

How about an off-frequency Cuban? True, that island is way south of you, but it still would be nighttime there.....
Click to expand...
It was a steady high squealy tone. Wish I'd have recorded it for a couple of minutes, but I was driving. Maybe heterodyne is the wrong word. But, judged against the Chicago clears, it was only against 780.
There are two Cubans on 770 and two on 790. Would they be that far off?
 


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