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- Direction_finding abstract "Direction finding (DF), or radio direction finding (RDF), is the measurement of the direction from which a received signal was transmitted. This can refer to radio or other forms of wireless communication, including radar signals detection and monitoring (ELINT/ESM). By combining the direction information from two or more suitably spaced receivers (or a single mobile receiver), the source of a transmission may be located via triangulation. Radio direction finding is used in the navigation of ships and aircraft, to locate emergency transmitters for search and rescue, for tracking wildlife, and to locate illegal or interfering transmitters. RDF was important in combating German threats during both the WW-II Battle of Britain and the long running Battle of the Atlantic. In the former, the Air Ministry also used RDF to locate its own fighter groups and vector them to detected Germain raids.RDF systems can be used with any radio source, although very long wavelengths (low frequencies) require very large antennas, and are generally used only on ground-based systems. These wavelengths are nevertheless used for marine radio navigation as they can travel very long distances "over the horizon", which is valuable for ships when the line-of-sight may be only a few tens of kilometres. 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 until recently, a feature of most aircraft, but is now being phased out For the military, RDF is a key tool of signals intelligence. The ability to locate the position of an enemy transmitter has been invaluable since World War I, and played a key role in World War II's Battle of the Atlantic. It is estimated that the UK's advanced "huff-duff" systems were directly or indirectly responsible for 24% of all U-Boats sunk during the war. Modern systems often used phased array antennas to allow rapid beamforming for highly accurate results, and are part of a larger electronic warfare suite.Radio direction finders have evolved, following the development of new electronics. Early systems used mechanically rotated antennas that compared signal strengths, and several electronic versions of the same concept followed. Modern systems use the comparison of phase or doppler techniques which are generally simpler to automate. Early British radar sets were referred to as RDF, which is often stated was a deception. In fact, the Chain Home systems used large RDF receivers to determine directions. Later radar systems generally used a single antenna for broadcast and reception, and determined direction from the direction the antenna was facing.".
- Direction_finding thumbnail Radiotriangulation.jpg?width=300.
- Direction_finding wikiPageExternalLink ap_index.htm.
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- Direction_finding wikiPageRevisionID "683174876".
- Direction_finding wikiPageWikiLink AM_broadcasting.
- Direction_finding wikiPageWikiLink AM_radio.
- Direction_finding wikiPageWikiLink FLR-9.
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- Direction_finding wikiPageWikiLink Antenna_(electronics).
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- Direction_finding wikiPageWikiLink Battery_(electricity).
- Direction_finding wikiPageWikiLink Battle_of_Britain.
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- Direction_finding wikiPageWikiLink Category:Automatic_identification_and_data_capture.
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- Direction_finding wikiPageWikiLink International_Naval_Research_Organization.
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- Direction_finding wikiPageWikiLink Line-of-sight_propagation.
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- Direction_finding wikiPageWikiLink Multilateration.
- Direction_finding wikiPageWikiLink National_Physical_Laboratory_(United_Kingdom).
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- Direction_finding wikiPageWikiLink Radio_navigation.
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- Direction_finding wikiPageWikiLink Robert_Watson-Watt.
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- Direction_finding wikiPageWikiLink Royal_Navy.
- Direction_finding wikiPageWikiLink Search_and_rescue.
- Direction_finding wikiPageWikiLink Signaling_(telecommunication).
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- Direction_finding wikiPageWikiLink Time_(magazine).