how far AM frequency can travel?

Question

i was at greenville, sc and i was listening to the radio and i was able to pick WCBS 880 AM how is that possible?

Answer 1

May I assume it was at night?

When the sun goes down, energy being transferred to the ionosphere is greatly reduced, so the ionosphere "settles down to a nice calm "layer". This allows radio energy in the bands around the AM dial (Medium frequencies, they are called), up to the "high" frequency band around 10 MHz (10,000 on your AM dial if it were there), to bounce off the ionosphere cleanly and be reflected back to earth at great distances. During the day, these RF waves just "scatter".

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Answer 2

Radio waves directed out to space are reflected back to the ground by the ionosphere. They can therefore travel greater distance since they can be reflected back down over the horizon...

http://apollo.lsc.vsc.edu/classes/met130/notes/chapter1/ion2.html

Answer 3

I picked up a Texas station one night traveling through western Missouri. Depending on the weather, they can go a long way.

Answer 4

"Shortwave frequencies are capable of reaching any location on the Earth because they can be refracted by the ionosphere (a phenomenon known as Skywave propagation)."

http://en.wikipedia.org/wiki/Short_wave_radio