Editing Phased array (section)

=== Broadcasting ===
In [[broadcast engineering]], the term 'phased array' has a meaning different from its normal meaning, it means an ordinary [[array antenna]], an array of multiple [[mast radiator]]s designed to radiate a [[directional antenna|directional]] radiation pattern, as opposed to a single mast which radiates an [[omnidirectional antenna|omnidirectional]] pattern. Broadcast phased arrays have fixed radiation patterns and are not 'steered' during operation as are other phased arrays.

Phased arrays are used by many [[AM broadcasting|AM broadcast]] [[radio stations]] to enhance [[signal strength]] and therefore coverage in the [[city of license]], while minimizing [[Interference (communication)|interference]] to other areas. Due to the differences between daytime and nighttime [[ionosphere|ionospheric]] [[radio propagation|propagation]] at [[mediumwave]] frequencies, it is common for AM broadcast stations to change between day ([[groundwave]]) and night ([[skywave]]) radiation patterns by switching the [[phase (waves)|phase]] and power levels supplied to the individual antenna elements ([[mast radiator]]s) daily at [[sunrise]] and [[sunset]]. For [[shortwave]] broadcasts many stations use arrays of horizontal dipoles. A common arrangement uses 16 dipoles in a 4×4 array. Usually this is in front of a wire grid reflector. The phasing is often switchable to allow [[beam steering]] in azimuth and sometimes elevation.