Voice Communication

In order to allow transmission of voice, the voice frequencies have to be added to a high frequency carrier. The process of adding the voice frequencies is called modulation.
The amplitude of the carrier of broadcast stations is varied according to the voice signal. This is called Amplitude Modulation (AM).
Broadcast stations on VHF are using frequency modulation (FM). In this case, the carrier frequency is varied.
Amateur radio stations on shortwave mainly use a special modulation called Single Side Band modulation (SSB). This system reduces the required power by 75% as compared to AM.

	Listen to a voice call of an amateur radio station

	What is the difference between Amplitude- (AM), Single Sideband- (SSB) and Frequency Modulation (FM)?

AMATEUR RADIO