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Channel spacing, also known as bandwidth [citation needed], is a term used in radio frequency planning. It describes the frequency difference between adjacent allocations in a frequency plan . Channels for mediumwave radio stations, for example are allocated in internationally agreed steps of 9 or 10 kHz : 10 kHz in ITU Region 2 (the Americas ...
An FM radio receiver's tuner spans a limited range of frequencies. A government agency (such as the Federal Communications Commission in the United States) may apportion the regionally available bandwidth to broadcast license holders so that their signals do not mutually interfere. In this context, bandwidth is also known as channel spacing.
The original allocation of channels consisted of only channels 1 to 28 with 50 kHz spacing between channels, and the second frequency for full-duplex operation 4.6 MHz higher. Improvements in radio technology later meant that the channel spacing could be reduced to 25 kHz with channels 60 to 88 interspersed between the original channels.
Channel spacing for voice communication on the airband was originally 200 kHz until 1947, [9] providing 70 channels from 118 to 132 MHz. Some radios of that time provided receive-only coverage below 118 MHz for a total of 90 channels.
Frequency deviation is used in FM radio to describe the difference between the minimum or maximum extent of a frequency modulated signal, and the nominal center or 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.
A trunked radio system is a two-way radio system that uses a control channel to automatically assign frequency channels to groups of user radios. In a traditional half-duplex land mobile radio system a group of users (a talkgroup ) with mobile and portable two-way radios communicate over a single shared radio channel, with one user at a time ...
TETRA uses different channel spacing compared to GSM systems. The standard is 25 kHz spacing and the center frequency of each channel may be offset in a number of fashions such as ±12.5 kHz or even ±6.25 kHz. This makes it more tricky to correlate the ARFCN strictly to a pair of frequencies, you need to know the specifics of the system.
The rules for second-adjacent-channel spacing do not apply for stations licensed before 1964. In 2017, Brazil laid the groundwork to reclaim channels 5 and 6 (76.1–87.5 MHz) for sound broadcasting use and required new radio receivers to be able to tune into the new extended band (Portuguese: faixa estendida, abbreviated eFM).