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Topic: Radio direction finder

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	Radio direction finder - Wikipedia, the free encyclopedia
		RDF's work by pointing a directional antenna in "various directions" and then listening for the direction in which the signal from a known station came through most strongly.
		RDF antennas are particularly easy to spot on German World War II aircraft, as loops under the rear section of the fuselage, whereas most US aircraft enclosed the antenna in a small teardrop-shaped fairing.
		RDF was once the primary form of aircraft navigation, and strings of beacons were used to form "airways" from airport to airport.
	en.wikipedia.org /wiki/Radio_direction_finder (478 words)

	Radio Direction Finder - Wikipedia
		Een Radio Direction Finder of afgekort RDF (Nederlandse term: radiorichtingzoeker) is een apparaat waarmee de richting van de bron van een radiosignaal kan worden bepaald.
		RDF's werken door een richtingsgevoelige antenne in diverse richtingen te laten wijzen, en dan te bepalen uit welke richting het radiosignaal het sterkst wordt ontvangen.
		RDF's kunnen op twee manieren worden gebruikt: voor plaatsbepaling van de gebruiker, of voor plaatsbepaling van een ander doel dan de gebruiker zelf.
	nl.wikipedia.org /wiki/Radio_Direction_Finder (382 words)

	High sensitivity portable radio direction finder - Patent 4475106 (Site not responding. Last check: 2007-11-07)
		Radio direction finding apparatus as defined in claim 2 characterized in that said polarity determining means includes left and right display means, and means operable to activate each thereof simultaneously if there is virtually no direction finding output from said FM receiver thereby indicating that said antennae are in a null position.
		Radio direction finding apparatus ad defined in claim 4 characterized in that said aural means includes constant amplitude means operable independently of the audible output of said FM receiver and providing distinctive audible tones respectively indicative of the direction to rotate said antennae to achieve the preferred null of said monitored transmitter.
		The radio signal modulated by the switching antennae acts as a synchronous "transmitter", the receiver unit 7 is the communications channel which exhibits delay and noise, and the oscillator unit 8 and divider flip-flop unit 10 act as a reference for both the "transmitter" and the detector.
	www.freepatentsonline.com /4475106.html (3787 words)

	Radio direction finder -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-11-07)
		A radio direction finder, or RDF, is a device for finding the direction to a (A communication system based on broadcasting electromagnetic waves) radio source.
		Due to radio's ability to travel very long distances "over the horizon", it makes a particularly good (The guidance of ships or airplanes from place to place) navigation system for ships and aircraft that might be flying at long distances from land.
		RDF's work by pointing a directional (An electrical device that sends or receives radio or television signals) antenna in "various directions" and then listening for the direction in which the signal from a known station came through most strongly.
	www.absoluteastronomy.com /encyclopedia/r/ra/radio_direction_finder.htm (544 words)

	Station Information - Radio direction finder
		Due to radio's ability to travel very long distances "over the horizon", it makes a particularily good navigation system for ships and aircraft that might be flying at long distances from land.
		RDF's work by pointing a directional antenna in "various directions" and then listening for the source.
		RDF antennas are particularily easy to spot on German World War II aircraft, as loops under the rear section of the fuselage, whereas most US aircraft enclosed the antenna in a small teardrop-shaped fairing.
	www.stationinformation.com /encyclopedia/r/ra/radio_direction_finder.html (440 words)

	Direction - Wikipedia, the free encyclopedia
		A direction can be specified by a unit vector; the components are direction cosines; together with magnitude, direction can be specified by a vector in general.
		"Direction" is a term for a principle tool used in practicing the Alexander Technique.
		"Direction" is also the name of a major political party in Slovakia.
	en.wikipedia.org /wiki/Direction (183 words)

	Radio direction finder: Definition and Links by Encyclopedian.com - All about Radio direction finder (Site not responding. Last check: 2007-11-07)
		This sort of system was widely used in the 1930s and 1940s, and the antennas are easy to find on many German World War II aircraft, as loops under the rear section of the fuselage.
		In this system the antenna consists of a small cylinder of wire, a soleniod[?] that is highly directional, which is spun by a motor.
		Signals are provided in the form of radio beacons, the radio analog of a lighthouse.
	www.encyclopedian.com /di/Direction-finder.html (405 words)

	Radio direction finder - Patent 4368470 (Site not responding. Last check: 2007-11-07)
		A radio direction finder according to claim 1, wherein said display means includes a digital display unit and an analog display unit for displaying a bearing corresponding to the value displayed by said analog display unit.
		A radio direction finder according to claim 1, wherein the number of input pulses to said phase tracking counter is controlled by controlling the number of input pulses to higher or lower bit sections of said phase tracking counter.
		In the radio direction finder according to the present invention, a reference counter and a phase tracking counter for repeatedly counting a series of input pulses in synchronism to the period of substantial rotation of the directivity of an antenna means are provided.
	www.freepatentsonline.com /4368470.html (1844 words)

	Aerospace Science and Technology Dictionary R Page
		Radio astronomy measurements are usually of the intensity of the received signal but often include polarization of the signal and angular size of the source.
		Any radio transmitter, together with its associated equipment, that emits signals enabling the determination, by means of suitable receiving equipment, of direction, distance, or position with respect to the beacon.
		The process in which the direction of energy propagation is changed as the result of a change in density within the propagating medium, or as the energy passes through the interface representing a density discontinuity between two media.
	www.hq.nasa.gov /office/hqlibrary/aerospacedictionary/508/r.html (10294 words)

	* Radio direction finder - (Boating): Definition (Site not responding. Last check: 2007-11-07)
		The RDF is used with a to find a to help determine the vessel's position...
		Radio Direction Finder (RDF)- A radio receiver equipped...
		The radio beacon's position is known and the direction of the radio beacon can be determined by using a radio direction finder...
	www.mimihu.com /boating/radio_direction_finder.html (113 words)

	radio direction finder -- Encyclopædia Britannica (Site not responding. Last check: 2007-11-07)
		This direction, called a bearing, can be marked on the chart as a line passing through the identified reference point.
		The first radio aid to navigation was two-way communication with a transmitter and a receiver in the airplane and on the ground.
		Wind direction is indicated by a vane, a pointer that swings with the wind and is mounted on a vertical axis attached to a...
	www.britannica.com /eb/article-9062412 (884 words)

	The Merchant shipping (Site not responding. Last check: 2007-11-07)
		Installation of radio direction-finder—(l) The radio-direction finder shall be installed in such a position that efficient determination of radio bearings by means of the radio direction-finder will not be lied hindered by extraneous noises.
		(a) The radio direction finder aerial system referred to in the First Schedule shall be mounted in such a manner that the efficient determination of radio bearings by means of the radio direction-finder is hindered as little as possible by the proximity of aerial, derricks, 01’ wire halyards, or other large metal objects.
		Calibration—(1) The Master of every ship shall cause the radio direction finder to be calibrated in accordance with this rule as soon as practicable after it has been installed in the ship and whenever any change is made in the position of the radio direction finder aerial system.
	dgshipping.nic.in /rules/radio_dir_fin_1968.htm (3773 words)

	Photo of Radio Direction Finder - National Institute of Standards and Technology Virtual Museum (Site not responding. Last check: 2007-11-07)
		The radio direction finder was a special antenna that determined the direction of radio transmissions.
		Built in 1916, it served as a prototype for the U.S. Navy and was used widely to pinpoint the positions of enemy forces during WWI.
		By the mid-1920s, many civilian vessels were outfitted with the "radio compass" as it came to be known.
	museum.nist.gov /panels/gallery/radiodf.html (156 words)

	Howeth: Chapter XXII (1963)
		Little was known of the radio deviation caused by the closed-looped circuits inherent in ship construction, and these deviations were not compensated for and caused large errors in the bearings obtained.
		The sole purpose of a radio direction finder installation is to provide the means of determining the bearings of a radio transmitter emitting signals.
		German submarine commanders, unaware of the use of direction finders, continued the unrestricted use of radio and allowed themselves to be constantly tracked.
	earlyradiohistory.us /1963hw22.htm (2522 words)

	Radio direction finding vehicle tracking systems
		An ACTIVE station is one who obtains an RDF (Radio Direction Finding) bearing to the target, displays the bearing on his own mapped screen, and telemeters his bearings via the packet data link to other stations on the net.
		At the same time, he is receiving RDF bearings over the data link from other stations in the net, all of which display on his screen also.
		Frequently, handheld radios can be used in applications where space and power is at a premium, such as a manportable RDF node.
	www.swssec.com /tracknet.html (1584 words)

	Heathkit Virtual Museum \| DF-1 (Site not responding. Last check: 2007-11-07)
		The Heathkit Transistor Radio Direction Finder model DF-1 is a self-contained, self-powered, super heterodyne broadcast radio receiver incorporating six name brand (Texas Instrument) transistors, a directional loop antenna, indicating meter, and integral speaker.
		A directional high-Q ferrite antenna is incorporated which is rotated from the front panel by a nylon right-angle gear drive to obtain a fix on a station.
		To find the direction of a station you set the sensitivity control and rotate the antenna for maximum reading on the null portion of the meter.
	www.heathkit-museum.com /other/df-1.shtml (559 words)

	Transmitter Hunting (Site not responding. Last check: 2007-11-07)
		Radio-direction-finding (RDF), also called transmitter hunting or"fox"-hunting, is a method of using radio-direction-finding techniques to find the location of a radio transmitter.This facet of Amateur Radio has both a serious and a fun side (neither of which involve the pursuit of any furry woodland creatures).
		RDF techniques have been used by Amateurs to locate sources of radio-frequency interference (RFI), unintentional or otherwise, to Amateur Radio and other radio services, such as municipal fire department and law enforcement radio communications systems.
		Directional antennas for this band are reasonably small and portable enough to use for tracking on foot or from a vehicle, and are easy to build.
	webhome.idirect.com /~griffith/rdf.htm (629 words)

	RADIO DIRECTION FINDER (Site not responding. Last check: 2007-11-07)
		A radio-receiving set, together with its associated equipment, used to determine the direction from which a radio signal is transmitted.
		This instrument was the reading device of a radio direction finder that would allow a ship or aircraft to home in on a radio signal and determine the direction to the transmitter.
		Note what appears to be a large radio direction finder amidships.
	www.websters-online-dictionary.org /ra/radio+direction+finder.html (744 words)

	Radio Direction Finder
		A boat with a directional antenna can determine its present position with the help of readings from local beacons.
		The course is the direction of travel of the boat and is measured in degrees clockwise from north.
		The relative bearing of a beacon is given in degrees clockwise relative to the course of the boat.
	acm.uva.es /p/v2/217.html (491 words)

	Dick Smith K-6345 Improvements (Site not responding. Last check: 2007-11-07)
		Voice or tone modulation on the signal being hunted caused a "spreading" of the direction indication, frequently causing it to light all the LEDs in the circle on modulation peaks.
		Primary advantages of the Doppler RDF technique over beam/quad/loop schemes are that Doppler sets are easier to use in motion and they average out multipath indications.
		When it comes to pinpointing the source of malicious QRM and gathering credible evidence, there is no substitute for a cadre of mobile hunters who have practiced their skills and become familiar with their gear.
	members.aol.com /homingin/DSEfix.html (2941 words)

	Radio Direction Finder Antenna Systems
		The VHF direction finder (VDF) uses the transmitted signal to determine the bearing to the target transmitter; the bearing is determined by evaluating the angle at which the RF wavefront passes over the VDF antenna site.
		As part of the development effort of direction finders and the several antenna alternatives, there has been some very useful mathematical analysis of the effects of reflections on various systems.
		Obviously, its slight increase in annualized cost over a lesser antenna is a small price to pay to achieve the primary, and indeed the only mission of a Radio Direction Finder, the timely and accurate location of a pilot and his aircraft in an emergency situation.
	www.servo.com /radio.htm (1612 words)

	Dictionary of Technical Terms for Aerospace Use - R (Site not responding. Last check: 2007-11-07)
		radio waves for detecting, locating, or tracking objects (such as rockets), for measuring altitude, etc., in any of various activities, such as air traffic control or guidance.
		radio waves from the craft and the reception of the same waves reflected from the terrain.
		resolution of a directional radio system can be different from the resolving power of its antenna, since the resolution is affected by other factors.
	www.jsc.nasa.gov /er/seh/r.html (10646 words)

	Radio Direction Finder (Site not responding. Last check: 2007-11-07)
		You can pay more but all you need is the "SEARCHER." A direction finder antenna that connects to any UHF/VHF Amateur Radio or Scanner.
		Tune your radio to the frequency of the transmitter you are trying to locate (from 140 MHz to 500 MHz), you will hear a tone and the transmit modulation at the same time.
		When the tone nulls (becomes silent) that is the direction you want to travel.
	www.transeltech.com /ERI/SDF-1.html (140 words)

	RF Products Radio Direction Finder Applications Literature Index and Downloads
		RDF Products publishes a variety of applications literature both to aid users in their selection of new radio direction finding products as well as to help users more effectively deploy and operate their existing radio direction finding equipment:
		RDF Products also publishes Application Notes to help illuminate various aspects of radio direction finding technology.
		Discusses the relative merits of Adcock and loop DF Antennas for fixed-site radio direction finding applications using a 30 MHz installation as an example.
	www.rdfproducts.com /ap_index.htm (681 words)

	MSN Encarta - Search Results - direction finder
		An electronic navigation instrument called a radio direction finder (RDF) takes bearings on radio beacons, many of which are in lighthouses and...
		1953: Radio And Radar : Radio Direction Finder.
		Round the magnitude to one decimal place and the direction to the nearest degree.
	encarta.msn.com /direction+finder.html (243 words)

	DOPPLER DF INSTRUMENTS/PRINCIPLES
		Because it is a form of frequency modulation, an FM receiver is required to detect it.
		no internal modifications of the radio are required.
		Switching between 8 stationary antennas does not produce the same type of Doppler shift that would be produced by a single antenna, moving in a circle.
	www.silcom.com /~pelican2/PRINCIPLES.html (723 words)

	Wullenweber Direction Finder (Site not responding. Last check: 2007-11-07)
		In operation, 40 contiguous dipoles at a time were connected to a radio receiver at the center of the ring, thus forming a highly directive receiving antenna array.
		By monitoring the output of the radio receiver as the array was scanned, the direction of arrival of a particular radio signal could be determined.
		By correlating the measurements from two or more of them, the location of a particular radio transmitter (and thus of the ship or installation containing it) could be determined.
	www.ece.uiuc.edu /pubs/wullen/wullart.htm (252 words)

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