AM radio uses the ionosphere to " skip" the signal to a much larger area.
But the skip doesn't work all the time.
At home, on my base station, I could talk 200 miles without the skip...the Moonraker 6 antenna was huge (15' long?) . With the skip running I could talk to Mexico, central America, etc.
Today there is so much traffic on the regular 40 channels that it's a mess. But above and below is still pretty good...but not FCC approved.
