Matches in DBpedia 2015-10 for { <http://dbpedia.org/resource/Radio_direction_finder> ?p ?o }
- Radio_direction_finder abstract "A radio direction finder (RDF) is a device for finding the direction, or bearing, to a radio source. The act of measuring the direction is known as radio direction finding or sometimes simply direction finding (DF). Using two or more measurements from different locations, the location of an unknown transmitter can be determined; alternately, using two or more measurements of known transmitters, the location of a vehicle can be determined. RDF is widely used as a radio navigation system, especially with boats and aircraft.RDF systems can be used with any radio source, although the size of the receiver antennas are a function of the wavelength of the signal; very long wavelengths (low frequencies) require very large antennas, and are generally used only on ground-based systems. These wavelengths are nevertheless very useful for marine navigation as they can travel very long distances and "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, often tuned to commercial AM radio broadcasters, is a feature of almost all modern aircraft.For the military, RDF systems are a key component of signals intelligence systems and methodologies. The ability to locate the position of an enemy broadcaster has been invaluable since World War I, and play 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 beam forming for highly accurate results. These are generally integrated into a wider electronic warfare suite.Several distinct generations of RDF systems have been used over time, following the development of new electronics. Early systems used mechanically rotated antennas that compared signal strengths in different directions, 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. Modern pseudo-Doppler direction finder systems consist of a number of small antennas fixed to a circular card, with all of the processing occurring in software.Early British radar sets were also referred to as RDF, which was a deception tactic. However, the terminology was not inaccurate; the Chain Home systems used separate omni-directional broadcasters and large RDF receivers to determine the location of the targets.".
- Radio_direction_finder thumbnail Earhart-electra_10.jpg?width=300.
- Radio_direction_finder wikiPageExternalLink Learning_RMI_Sim_1.aspx.
- Radio_direction_finder wikiPageID "192108".
- Radio_direction_finder wikiPageLength "30437".
- Radio_direction_finder wikiPageOutDegree "106".
- Radio_direction_finder wikiPageRevisionID "680899115".
- Radio_direction_finder wikiPageWikiLink AM_broadcasting.
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- Radio_direction_finder wikiPageWikiLink Acronyms_and_abbreviations_in_avionics.
- Radio_direction_finder wikiPageWikiLink Adcock_antenna.
- Radio_direction_finder wikiPageWikiLink Amateur_radio_direction_finding.
- Radio_direction_finder wikiPageWikiLink Antenna_(electronics).
- Radio_direction_finder wikiPageWikiLink Antenna_(radio).
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- Radio_direction_finder wikiPageWikiLink Battle_of_the_Atlantic.
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- Radio_direction_finder wikiPageWikiLink Bearing_(navigation).
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- Radio_direction_finder wikiPageWikiLink Category:Aids_to_navigation.
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- Radio_direction_finder wikiPageWikiLink Category:American_inventions.
- Radio_direction_finder wikiPageWikiLink Category:Avionics.
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- Radio_direction_finder wikiPageWikiLink Category:Radio_navigation.
- Radio_direction_finder wikiPageWikiLink Chain_Home.
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- Radio_direction_finder wikiPageWikiLink US_Navy.
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