From HF Underground
SSB, or single sideband, is a mode of transmission where the carrier and one sideband is suppressed; only one sideband remains. This is the mode used most frequently by amateur radio operators, and thus, has also become somewhat of a standard for pirates.
The primary advantage is efficiency. At least one half of the power of an AM transmitter goes into producing the carrier, which carries no information. Up to one quarter of the power goes into each sideband. By eliminating the carrier and transmitting just one sideband, only one quarter of the transmitter power is required. Or, looking at it another way, four times as much power is available for producing the remaining sideband.
The main disadvantage of SSB is that since no carrier is present, correct tuning of the station is critical. Any tuning error will result in all of the audio tones being off by the amount of the error. This is acceptable for speech, but in the case of music, results in extremely unpleasant audio.
SSB has been nicknamed Satan Side Band, due to the poor audio quality usually rendered when broadcasting music. On the other hand, it has also been referred to as "the manliest of modes", primarily by He-Man Radio.