Single-sideband transmission

Single-sideband transmission is a method of transmitting audio based on amplitude modulation. Essentially, the carrier and one sideband of an AM signal are removed, leaving only the opposite sideband. This reduces the signal bandwidth needed and increases effective power output, as the carrier and redundant sideband account for well over half of the power output of an AM transmitter.

Since there is no carrier, the signal must be mixed with steady tone beat signal of a proper frequency to be demodulated on the receiving end. Thus, a SSB signal cannot be demodulated by standard AM receivers.

SSB was pioneered by long distance telephone companies in the 1930's for wired use and began to be seriously experimented with by radio amateurs directly after the second world war. It has grown into a de facto standard for long distance voice radio transmissions since then.