Direction finding
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Direction finding, radio direction finding, or radiogoniometry is the use of radio waves to determine the direction to a radio source. The source may be a cooperating radio transmitter or may be an in
Radiotriangulation scheme using two direction-finding antennas (A and B)
Direction finding antenna near the city of Lucerne, Switzerland
W.G. Wade of the National Bureau of Standards uses a large multi-loop antenna to perform RDF in this 1919 photo. This is a fairly small unit for the era.
This Royal Navy model is typical of B–T goniometers. The two sets of "field coils" and the rotating "sense coil" are visible.
Automatic direction finder
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An automatic direction finder is a marine or aircraft radio-navigation instrument that automatically and continuously displays the relative bearing from the ship or aircraft to a suitable radio statio
Direction finding
…For aerial use, where the horizon may extend to hundreds of kilometres, higher frequencies can be used, allowing the use of much smaller antennas. An automatic direction finder, which could be tuned to radio beacons called non-directional beacons or commercial AM radio broadcasters, was in the 20th century a feature of most…
A teardrop-shaped housing that encases LP-21 rotatable loop antenna attached to the underside of Douglas DC-3 "Flagship Knoxville". The loop antenna is used for the ADF.