My brother swears he can get Chicago’s ESPN Radio 1000AM in and around Philly at night. I was skeptical, but then I looked it up on Wikipedia:
Medium wave and short wave radio signals act differently during daytime and nighttime. During the day, AM signals travel by groundwave, diffracting around the curve of the earth over a distance up to a few hundred miles (or kilometers) from the signal transmitter. However, after sunset, changes in the ionosphere cause AM signals to travel by skywave, enabling AM radio stations to be heard much farther from their point of origin than is normal during the day.
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One response to “Chicago AM Stations Heard in Philly?”
Ah yes, one of the many useful things I learned in flight school. Some navigational instruments work on AM radio signals, so those were much stronger at night, too.
The bonus was that since those instruments picked up AM frequencies, you could listen to AM radio while you were flying by tuning in and hitting the IDENT button…and AM radio out west is entertainingly wacky.