AM stands for amplitude modulation, which is a method of encoding the audio signal on the carrier frequency. It was the first method developed for making audio radio transmissions and is still used worldwide, primarily for medium wave transmissions, but also on the longwave and shortwave radio bands. AM radio stations are also sometimes referred to as "standard broadcast stations" because AM was the first form used to transmit broadcast radio signals to the public. The key features of AM radio include:
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Amplitude modulation: The information (audio waves or digital data) is transmitted in variations in the amplitude of the carrier wave.
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Frequency range: AM radio ranges from 535 to 1705 kilohertz.
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Sky wave propagation: Many AM stations are either daytime-only stations or stations authorized to operate at very low power levels at night as a result of “sky wave” propagation, which occurs when the AM signal is reflected off the ionosphere and back to the earth.
Compared to FM radio, AM radio has a lower sound quality and is more susceptible to static and interference. However, AM radio remains an integral part of many lives as a means of communication in third-world countries.
