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AM Radio waves
Nov. 4th, 2017 07:57 pmПобачив випадково, зацікавився, залишу тут.
"AM waves during the day pass through the ionosphere, causing them to not travel as far, and so AM signals during the day that you can hear are ground waves - essentially, line-of-sight radio waves. At night, the ionosphere doesn't absorb AM signals, it reflects them, so they can travel an amazingly long way - they literally bounces off the sky, off the ground, off the sky again, off the ground, etc. Radio stations thus must reduce their signals or else they'll interfere with one another." http://boards.straightdope.com/sdmb/showthread.php?t=391660
"Most AM radio stations are required by the FCC's rules to reduce their power or cease operating at night in order to avoid interference to other AM stations." http://www.fcc.gov/media/radio/am-stations-at-night
"AM waves during the day pass through the ionosphere, causing them to not travel as far, and so AM signals during the day that you can hear are ground waves - essentially, line-of-sight radio waves. At night, the ionosphere doesn't absorb AM signals, it reflects them, so they can travel an amazingly long way - they literally bounces off the sky, off the ground, off the sky again, off the ground, etc. Radio stations thus must reduce their signals or else they'll interfere with one another." http://boards.straightdope.com/sdmb/showthread.php?t=391660
"Most AM radio stations are required by the FCC's rules to reduce their power or cease operating at night in order to avoid interference to other AM stations." http://www.fcc.gov/media/radio/am-stations-at-night