(Frequency Modulation radio) Radio broadcasting in the 88-108 MHz frequency band. In the former Soviet countries and Japan, the 65-74 and 76-95 MHz bands are used respectively. FM technology modulates a carrier by varying the frequency, not by signal strength as with AM. Developed in the 1930s, FM became popular in the late 1950s for music listening due to its greater fidelity than AM. Transmitting FM in stereo began in the 1960s. See AM radio and shortwave radio.