FM frequency is widely used in telecommunication devices to transmit voice without disturbances. Its important feature is the Resilience to signal level variations. The modulation is carried only as variations in frequency. That is, any signal level variations will not affect the audio output, provided that the signal does not fall to a level where the receiver cannot cope. FM wave has property of resilience to noise and interference. It is for this reason that FM is used for high quality broadcast transmissions.
Frequency modulation (FM) is the method of conveying informations over a carrier wave by varying its frequency. FM broadcasting is a broadcast technology invented by Edwin Howard Armstrong to provide high-fidelity sound transmission over broadcast radio. The history of FM dates back to 1936 when Edwin Howard Armstrong described the FM frequency as a method of reducing disturbances in radio transmission in a conference of Radio Engineers New York in November 6, 1936.
Throughout the world, the broadcast band falls within the VHF part of the radio spectrum. Usually 88 – 108 MHz is used. The range of an FM mono transmission is related to the transmitter RF power, the antenna gain and antenna height.For FM stereo, the maximum distance covered is significantly reduced. This is due to the presence of the 38 kHz sub carrier modulation. Vigorous audio processing improves the coverage area of an FM stereo station.
FM is commonly used at VHF radio frequencies for high-fidelity broadcasts of music and speech. Normal TV sound is also broadcast using FM. The FM band used in broadcast is generally called wide-FM, or W-FM. In two-way radio, Narrowband-FM (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into space.