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Horizontal plane

Horizontal plane is used in radio to plot a antenna's relative field strength (which directly affects a station's coverage area) on a polar graph.

Normally the maximum of 1.000 or 0dB is at the top, which is labeled 0o, running clockwise back around to the top at 360o. Other field strengths are expressed as a decimal less than 1.000, a percentage less than 100%, or decibels less than 0dB. If the graph is of an actual or proposed installation, rotation is applied so that the top is 0o true north.

See also the perpendicular vertical plane.