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Jul 25, 2005, 01:05 AM
Rem The Wasp CV-7 9/15/42
SammyB's Avatar

Why does AM radio reception diminish at night?


Atleast it does where I live. Right as the sun starts to go down, the radio stations will fade more and more until you hear nothing. Anyone know why?
Jul 25, 2005, 01:41 AM
Thanks for the Fish!
aerogel's Avatar
weird I know the sun's ionizes layers and the earth's atmosphere will prevents am propagation...where is this station is it day there?
Jul 25, 2005, 01:41 AM
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Steve Guinn's Avatar
"Many stations power down to 250 watts during the night. This is to protect the class A stations from interference."

Here's a link...
http://www.mcps.k12.md.us/department...s/amradio.html
Jul 25, 2005, 01:42 AM
Rem The Wasp CV-7 9/15/42
SammyB's Avatar
The station is based in the Los Angeles area. It is night here now.
Jul 25, 2005, 01:45 AM
Thanks for the Fish!
aerogel's Avatar
Steve for like clear channles?
Jul 25, 2005, 01:49 AM
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Steve Guinn's Avatar
The little local station's signal travels much further at night. They cut power to keep from interfering with the big boys.
Jul 25, 2005, 02:09 AM
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LTChip's Avatar
The reach of the signal is further at night so many stations power back their transmitters so as not to interfere with other markets. I can get LA stations on my car's AM radio when I am up in Tahoe at night.

http://www.fcc.gov/mb/audio/bickel/daytime.html better explaination from the source.
Jul 25, 2005, 11:42 AM
Eye Drather Beef Lying
ElectRick's Avatar
I can remember as a kid growing up in Georgia, that I could pick up WLS in Chicago at night on my tabletop AM radio. That always used to fascinate me.

Rick
Jul 25, 2005, 11:50 AM
Rem The Wasp CV-7 9/15/42
SammyB's Avatar
If people are getting LA stations in Tahoe, why can't I get LA stations in LA!
Jul 25, 2005, 12:17 PM
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Steve Guinn's Avatar
Because they are receiving the skywave signals while you are receiving the ground wave signals.

All those "powered down" stations combine to make white noise and drown everything out.
Jul 25, 2005, 06:49 PM
Procrashtinating Builder
mastrsn's Avatar
Quote:
Originally Posted by SammyB
Atleast it does where I live. Right as the sun starts to go down, the radio stations will fade more and more until you hear nothing. Anyone know why?

Any Ham radio operator will tell you that the atmosphere at night is perfect for recieving radio signals.....

If you were a CB'r in the day, do you remember listening to the radio and getting "skip" from other states?

We have a 50,000 watt blow torch AM station, WOKV, here in Jacksonville, Florida that, by FCC rules, has to "power down" at 8:00pm so as to not interfere with Cuban radio. You can still hear it, but it is faint and you can hear the Cuban stations quite well.

I believe that they decrease their output so as not to bleed on another station at night due to the better reception. This is an FCC rule, not by the radio station's choice......


Still kinda neet to turn on the AM radio or the CB and Ham radio and see how far away you can hear.................


And being a Ham operator, I should know better to...

"Look out for those pesky Lightpoles!"
BB
Jul 25, 2005, 08:11 PM
Registered User
I worked the night shift at a new/motivation radio network years ago and one of the specific duties taught to me by the station manager was to turn down the station's power at a specific time.

AM will travel further at night, bouncing off the upper atmosphere, and if you don't power down you'll interfere with other stations using the same frequency in other areas of the country.

Got reamed one morning when I forgot and never forgot again... :-)
Jul 25, 2005, 08:17 PM
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Steve Guinn's Avatar
Hey Tim,

do you know anything about "Hot Rize" biscuits?
Jul 25, 2005, 08:24 PM
Rem The Wasp CV-7 9/15/42
SammyB's Avatar
so because I am close to the station, when they turn it down, I can't receive it but others far away can because it bounces off the atmosphere?
Jul 25, 2005, 08:51 PM
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Steve Guinn's Avatar
...


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