direction finder(redirected from D/F)
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direction finder,electronic device used to determine the position of a ship or aircraft. In a simple direction finder a radio receiver is equipped with a revolving directional antenna. The antenna receives the strongest radio signal when it is pointing directly at a transmitter. By determining the direction of two land-based transmitters, a navigator may plot his position by triangulation. Direction finders have been replaced in many applications with more accurate systems, such as radarradar,
system or technique for detecting the position, movement, and nature of a remote object by means of radio waves reflected from its surface. Although most radar units use microwave frequencies, the principle of radar is not confined to any particular frequency range.
..... Click the link for more information. and satellite navigation systems (see satellite, artificialsatellite, artificial,
object constructed by humans and placed in orbit around the earth or other celestial body (see also space probe). The satellite is lifted from the earth's surface by a rocket and, once placed in orbit, maintains its motion without further rocket propulsion.
..... Click the link for more information. ).
an instrument used in marine and air navigation to determine the direction in degrees to external reference points such as coastal or floating objects, heavenly bodies, and so on.
direction finder[də′rek·shən ‚fīnd·ər]
direction finder (DF)
A radio receiver equipped with a directional sensing antenna used to take bearings on a radio transmitter. Specialized radio direction finders are used in aircraft as air navigation aids. Others are ground based, primarily to obtain a “fix” on a pilot requesting orientation assistance or to locate downed aircraft. UDFs (ultrahigh frequency direction finders) receive signals in the ultrahigh frequency radio broadcast band; VDFs in the very high frequency band; and UVDFs (UHD/VHD direction finder) in both bands. See automatic direction finder.