Frequency deviation
Frequency deviation is used in FM radio to describe the maximum difference between an FM modulated frequency and the nominal carrier frequency. The term is sometimes mistakenly used as synonymous with frequency drift, which is an unintended offset of an oscillator from its nominal frequency.
The frequency deviation of a radio is of particular importance in relation to bandwidth, because less deviation means that more channels can fit into the same amount of frequency spectrum. The FM broadcasting range uses a channel spacing of 200 kHz, with a maximum frequency deviation of 75 kHz, leaving a 50 kHz buffer above the highest and below the lowest frequency to reduce interaction with other channels. AM broadcasting uses a channel spacing of 10 kHz in the U.S. and 9kHz in most other countries, 5 kHz, 2.5 kHz, and 2 kHz.
