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FM receivers employ a special detector for FM signals and exhibit a phenomenon known as the capture effect, in which the tuner "captures" the stronger of two stations on the same frequency while rejecting the other (compare this with a similar situation on an AM receiver, where both stations can be heard simultaneously).
FM radio on the new band had to begin from the ground floor. As a commercial venture, it remained a little-used audio enthusiasts' medium until the 1960s. The more prosperous AM stations, or their owners, acquired FM licenses and often broadcast the same programming on the FM station as on the AM station ("simulcasting"). The FCC limited this ...
With the gradual clearance of other users (notably Public Services such as police, fire and ambulance) and the extension of the FM band to 108.0 MHz between 1980 and 1995, FM expanded rapidly throughout the British Isles and effectively took over from LW and MW as the delivery platform of choice for fixed and portable domestic and vehicle-based ...
AM broadcasting is radio broadcasting using amplitude modulation (AM) transmissions. It was the first method developed for making audio radio transmissions, and is still used worldwide, primarily for medium wave (also known as "AM band") transmissions, but also on the longwave and shortwave radio bands.
AM detectors cannot demodulate FM and PM signals because both have a constant amplitude. However an AM radio may detect the sound of an FM broadcast by the phenomenon of slope detection which occurs when the radio is tuned slightly above or below the nominal broadcast frequency. Frequency variation on one sloping side of the radio tuning curve ...
A period of allowing existing FM stations to broadcast on both the original "low" and new "high" FM bands followed, which ended at midnight on January 8, 1949, at which time all low band transmissions had to end. [18] In 1978 one additional frequency reserved for educational stations, 87.9 MHz, was allocated. [19]
The band Grateful Dead and their concert "Great Canadian Train Ride" in 1970 was the first TV broadcast of a live concert with FM simulcast. In the 1970s WPXI in Pittsburgh broadcast a live Boz Scaggs performance which had the audio simultaneously broadcast on two FM radio stations to create a quadrophonic sound, the first of its kind.
The FCC gave FM two boosts in the early 1960s: first by setting a technical standard for stereo broadcasts, and second by adopting the FM Non-Duplication Rule in 1964, prohibiting broadcasters with an AM and FM license in cities of more than 100,000 from transmitting more than 50% of the same programming on both stations. [16]