|D/F, Abbreviation: DF a highly directional aerial system that can be used to determine the direction of incoming radio signals, used esp as a navigation aid|
|a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.|
|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
radio receiver and antenna system for determining the direction of the source of a radio signal. A direction finder (DF) can be used by an aircraft or ship as a navigational aid. This is accomplished by measuring the direction (bearing) of at least two transmitters whose locations are already known. When the measured directions from each transmitter are plotted on a map, the intersection of the two plotted lines gives the location of the aircraft or ship carrying the DF. This technique, using the directions to two or more transmitters of known location, is called triangulation.
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