Frequency Band

Frequency band, also called waveband, is a range of radio frequencies set aside for a single broadcasting station. A station's transmitter produces a certain constant carrier frequency. But the information being transmitted, such as sound or a TV picture, slightly modulates (changes) the carrier frequency. Because of this modulation, each station must use a range of frequencies for its broadcasts. For example, most amplitude modulation (AM) stations require a frequency band of 5 kilohertz above and below the carrier frequency of their transmitters. One kilohertz equals 1,000 hertz (cycles per second). The use of frequency bands keeps nearby stations from interfering with one another's broadcasts.

Frequency band also refers to any group of radio frequencies used for one purpose, such as commercial, ship-to-shore, amateur, airplane, or police broadcasting. In the United States, the Federal Communications Commission (FCC) assigns frequency bands. For example, in commercial broadcasting, the frequency band for AM stations ranges from 535 to 1,705 kilohertz. The range for frequency modulation (FM) stations is from 88 to 108 megahertz. One megahertz equals 1 million hertz. TV stations use several bands in the very high frequency (VHF) and ultrahigh frequency (UHF) ranges.

Contributor: Hugh D. Young, Ph.D., Prof. of Physics, Carnegie-Mellon Univ.

Frequency Band

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