(Some of) The Science Behind AM Radio

If you're at all curious about how AM radio works, radio historian and author, Michael Keith explained it to me this way:  "After sunset, an ionosphere layer forms, and what that does is it causes AM radio signals to bounce off it and go greater distances.... AM signals had the capacity to reach great distances because of atmospheric conditions after, after sun, after sunset. But you go back to the forties and fifties. You had 50, 000 watt AM stations, and they were clear channel stations, which meant that any stations that were on their frequency at 950 AM or whatever had to get out of their way at night. They had sovereignty. So if you were WBZ at 1030 in Boston at 50, 000 watts, At night, you owned that frequency and you had 50, 000 watts being piped out of your transmitter, so that signal, I mean, I traveled, in the Midwest, listening to WBZ in Boston, an AM radio station in Boston, I could hear in Indiana, Illinois, Iowa, and it would go to the Rocky Mountains. So, even though FM has better audio quality, less noise and can support stereo, AM has its advantages. For the reasons Michael laid out, it travels further and requires less infrastructure. So, that's partially why for decades, even after FM radio became popular, talk radio ruled the air waves." That's why talk show hosts such as Art Bell could gain a nationwide following, even though his show aired at 3 am. More of Michael's Interview will be featured in Part Two: Always On