FM broadcasting is a method of radio transmission using frequency modulation (FM) technology. Invented in 1933 by American engineer Edwin Armstrong, it is used worldwide to provide high-fidelity radio broadcast sound. FM broadcasting is capable of better sound quality than AM broadcasts, the head of the competition for radio transmission technology, it is used for most music broadcasts. FM radio stations use VHF frequencies. The term “FM band” describes the frequency band in a country devoted to FM broadcasting.
Worldwide, the FM broadcast band falls into the VHF band. Usually 87.5-108.0 MHz is used, or a part of it, with few exceptions:
The former Soviet republics, and some countries of the former eastern bloc, also used the band 65-74 MHz plus. Frequencies are allocated at 30 kHz intervals. This band, sometimes called band OIRT, is slowly being eliminated in many countries. The countries in the band 87.5 to 108.0 MHz is referred to as the CCIR band.
In Japan, the band 76-95 MHz is used.
The frequency of an FM broadcasting station (more strictly its rated nominal center frequency) is generally an exact multiple of 100 kHz. In most of South Korea, the Americas, the Philippines and the Caribbean, using odd multiples. In some parts of Europe, Greenland and Africa, that even multiple are used. In the United Kingdom, they are used even or odd. In Italy, they are used at a multiple of 50 kHz.
There are other unusual and obsolete FM broadcasting standards in some countries, including 1, 10, 30, 74, 500 and 300 kHz. However, in order to minimize interference between channels, stations that operate by the same or geographically close to the transmitting sites tend to maintain at least one frequency separation of 500 kHz, even when the nearest spacing frequency is technically permissible , With closer tuning reserved for several signal transmitters up to potentially interfering spaced are already more attenuated and therefore have less effect on neighboring frequencies.