| About 30 minutes ago I was driving back to Greensboro from my moms house. I was bored with about all of the cds in my car, so I opted to listen to the radio. For me this doesn't happen often. The only presets I have set are the ones corresponding to presets on the FM transmitter for my ipod. I didn't really find anything on the radio I wanted to listen to. For some reason I thought it would be a cool idea to switch over to the AM band. I don't think I have even heard anyone talk about listening to AM radio in a few years. Part of me wondered if it was even still around, and if it is what's on it now a days. It was mostly news. I stuck with one station for a while and realized they were broadcasting from New Orleans, and they weren't syndicated. After a few taps on the seek button, I heard the weather for Trenton, New Jersey. After seeking a bit more, I heard an advertisement for Chicago's public transportation. When I was younger my dad told me about how AM frequencies carried a lot farther at night, but I had always thought maybe this meant they stretched a few more miles or so. I didn't know the effect was this extreme. For the next few days or so, if I'm driving after dark, I'll probably be listening to AM radio.
Here's what wikipedia has to say about the subject:
During the daytime, medium and high powered mediumwave AM
radio stations have a normal reception range of about 20 to 250 miles
(32 to 400+ km), depending on the transmitter power, location, and the
quality of the receiving equipment, including the amount of man-made
and natural electromagnetic noise present. Long-distance reception is normally impeded by the D layer of the ionosphere, which during the daylight hours absorbs signals in the mediumwave range.
As the sun sets, the D-Layer dissipates, allowing Medium Wave radio waves from such stations to bounce off the ionosphere,
producing reliable, long distance reception of (especially)
high-powered stations up to about 1,200 miles (2,000 km) away on a
nightly basis. Aside from the more or less regular reception of certain
high powered transmitters, variable conditions allow reception of
different stations at different times - for example, on one night a
medium-powered broadcaster from Cleveland, Ohio
may be audible in Duluth, but not on the following night. Much of the
hobby consists in trying to receive and log as many of these stations
as possible, identifying target stations and frequencies to listen to
and log. |
