In broadcast engineering, directional array refers to an antenna array 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.
Famous quotes containing the word array:
“Any one who knows what the worth of family affection is among the lower classes, and who has seen the array of little portraits stuck over a labourer’s fireplace ... will perhaps feel with me that in counteracting the tendencies, social and industrial, which every day are sapping the healthier family affections, the sixpenny photograph is doing more for the poor than all the philanthropists in the world.”
—Macmillan’s Magazine (London, September 1871)