AM Radio Transmission at Night
Name: Ryne H.
How come distant AM radio stations come in better at
night then during the day? Local stations come in better during the day
then at night. Why?
Distant AM radio stations are better received at night because the
ionosphere that reflects AM stations is protected from ionizing radiation
and ionized particles from the Sun.
I am not sure local stations do come in better during the day than at
night -- at least I have not experienced that.
When the sun comes out, it sort of heats up the air, helping to make a part of
the air that can reflect radio waves, like the radio waves that come from
radio station. When the sun goes away at night, these parts of the
or air, change. So things can be different between the day time and the night
time. Radio waves can bounce around better during the night, when there
this extra part of the air reflecting waves around. Sunlight changes the
properties of the ionosphere.
Also, people know this, and make rules about how radio stations must work.
People say that some radio stations must cut their power at night, so as
interfere with far away places. But some radio stations can keep the same
power, or even go up at night. These clear channel radio stations then are
sending their night time signals all around, even out of the state.
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Update: June 2012