Directional array
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In broadcast engineering, directional array refers to multiple antennas arranged such that the superposition of the electromagnetic waves produce a predictable electromagnetic field. By spacing 2 or more antenna elements apart, changing the length of the transmission line from the transmitter, varying the power output, and shifting the phase, radio broadcasters can "shape" the area of signal coverage.
Geographically close co-channel or adjacent channel stations employ directional arrays (or a single directional antenna) so that other broadcasters may utilize the same or adjacent frequency. In the United States, the Federal Communications Commission offers a first-come, first-served approach, meaning licenses granted on co-channel or adjacent channels must protect the service contour of the previously licensed facility, thus, a directional array may be used to "shape" the station around existing facilities.
