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Encyclopedia > Yagi antenna
A Yagi-Uda antenna. From left to right, the elements mounted on the boom are called the reflector, driven element, and director. The reflector is easily identified as being a bit (5%) longer than the driven element, and the director a bit (5%) shorter.
A Yagi-Uda antenna. From left to right, the elements mounted on the boom are called the reflector, driven element, and director. The reflector is easily identified as being a bit (5%) longer than the driven element, and the director a bit (5%) shorter.

A Yagi-Uda Antenna, commonly known simply as a Yagi antenna or Yagi, is a directional antenna system consisting of an array of a dipole and additional closely coupled parasitic elements (usually a reflector and one or more directors). The dipole in the array is driven, and another element, 5% longer, operates as a reflector. Other shorter parasitic elements are typically added in front of the dipole as directors. This arrangement gives the antenna directionality that a single dipole lacks. Yagis are directional along the axis perpendicular to the dipole in the plane of the elements, from the reflector through the driven element and out via the director(s). If one holds out one's arms to form a dipole and has the reflector behind oneself, one would receive signals with maximum gain from in front of oneself. The top of a tower supporting a yagi and several wire antennas. ... The top of a tower supporting a yagi and several wire antennas. ... In a mutually coupled antenna array (notably a Yagi-Uda antenna), the driven element is the single antenna that has an applied source feed. ... A passive radiator or parasitic element is a radio antenna element which does not have any wired input. ... Log-periodic dipole array A directional antenna is an antenna which transmits or receives maximum power in a particular direction. ... A simple half-wave dipole antenna that a shortwave listener might build. ... A passive radiator or parasitic element is a radio antenna element which does not have any wired input. ... In a mutually coupled antenna array (notably a Yagi-Uda antenna), the driven element is the single antenna that has an applied source feed. ... An antenna reflector is a device that reflects electromagnetic waves. ... Log-periodic dipole array A directional antenna is an antenna which transmits or receives maximum power in a particular direction. ... In electronics, gain is usually taken as the mean ratio of the signal output of a system to the signal input of the system. ...


Directional antennas, such as the Yagi-Uda, are also commonly referred to as beam antennas.

Contents

Description

Yagi-Uda antenna. Viewed left to right: Reflector element, driven element, director element.
Yagi-Uda antenna. Viewed left to right: Reflector element, driven element, director element.
Yagi-Uda antenna signal-gathering action compared with other end-fire, back-fire and traveling-wave types.
Yagi-Uda antenna signal-gathering action compared with other end-fire, back-fire and traveling-wave types.

Yagi-Uda antennas include one or more director elements, which, by virtue of their being arranged at approximately a one-eighth-wavelength mutual spacing and being progressively slightly shorter than a half wavelength, direct signals of increasingly higher frequencies onto the active dipole. A reflector can mean one of several things: a reflecting telescope a device or a part of an antenna that reflects radio waves a device that causes reflection, for example, a mirror or a retroreflector a 1981 album by Pablo Cruise In LAPACK the term reflector with the types block... Look up element in Wiktionary, the free dictionary. ... In a mutually coupled antenna array (notably a Yagi-Uda antenna), the driven element is the single antenna that has an applied source feed. ... A passive radiator or parasitic element is a radio antenna element which does not have any wired input. ... Look up element in Wiktionary, the free dictionary. ... Image File history File links Antenna_boom_comparison. ... Image File history File links Antenna_boom_comparison. ... For other uses, see Wavelength (disambiguation). ...

Thus, the complete antenna achieves a distinct response bandwidth determined by the length, diameter, and spacing of all the individual elements; but its overall gain is proportional to its length, rather than simply the number of elements. Sources Federal Standard 1037C MIL-STD-188 Categories: Telecommunications stubs | Radio frequency antenna types ... Bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a filter, a communication channel, or a signal spectrum, and is typically measured in hertz. ...


All of the elements usually lie in the same plane, typically supported on a single boom or crossbar. The parasitic elements do not need to be coplanar, but can be distributed on both sides of the plane of symmetry. A set of points is said to be coplanar if and only if they lie on the same geometric plane. ... In 3-dimensional geometry, a plane of symmetry is a 2-dimensional flat dividing surface placed such that things on one side are symmetrical (mirror image) to things on the other side. ...


The antenna gain is a function of the number of dipole elements and can be approximated (for the main lobe) as

GT = 1.66 * N

Where N is the number of elements (dipoles) in the Yagi-Uda antenna


Developed Yagi-Uda antennas (including the one pictured) are designed to operate on multiple bands; the resulting design is made more complicated by the presence of a resonant parallel coil and capacitor combination (called a "trap" or LC) in the elements. A coil is a series of loops. ... See Capacitor (component) for a discussion of specific types. ... An LC circuit consists of an inductor, represented by the letter L, and a capacitor, represented by the letter C. When connected together, an electrical current can alternate between them at an angular frequency of where L is the inductance in henries, and C is the capacitance in farads. ...


Traps are used in pairs on a multiband antenna. The trap serves to isolate the outer portion of the element from the inner portion for the trap design frequency.


In practice, the higher frequency traps are located closest to the boom of the antenna. Typically, a triband beam will have 2 pairs of traps per element. For example, a typical triband Yagi-Uda beam covering the 10, 15 and 20 meter bands would have traps for the 10 and 15 meter bands.


The introduction of traps is not without cost—due to their nature, they reduce the overall bandwidth of the antenna and overall efficiency of the array on any given frequency, and radically affect its response in the desired direction.


Coverage example

Shown below is the coverage that could be provided by a 3- or 4-element Yagi-Uda array on the 41-meter shortwave radio broadcasting band. The transmitter driving the array has a power output of 20 kilowatts. The array's main lobe bearing is indicated by the red line from the proposed transmitter location in British Columbia, Canada. This predicted coverage was calculated by the VOACAP program.



Example of a Log Periodic Horizontal antenna used to cover 50% of Canada's landmass.
Image File history File links Size of this preview: 790 × 600 pixelsFull resolution (885 × 672 pixel, file size: 29 KB, MIME type: image/png) I am making these VOACAP HF area coverage calculations public so as to help users better understand the use of the VOACAP program. ...


History

The Yagi-Uda antenna was invented in 1926 by Shintaro Uda of Tohoku Imperial University, Sendai, Japan, with the collaboration of Hidetsugu Yagi, also of Tohoku Imperial University. Yagi published the first English-language reference on the antenna in a 1928 survey article on short wave research in Japan and it came to be associated with his name. However, Yagi always acknowledged Uda's principal contribution to the design, and the proper name for the antenna is, as above, the Yagi-Uda antenna (or array). Year 1926 (MCMXXVI) was a common year starting on Friday (link will display the full calendar) of the Gregorian calendar. ... This article is Tohoku University in Japan. ... Sendai ) is the capital city of Miyagi Prefecture, Japan, and the largest city in the Tōhoku (northeast) region. ... Hidetsugu Yagi (八木 秀次 Yagi Hidetsugu, January 28, 1886 - January 19, 1976) was a Japanese electrical scientist who wrote several important articles that led to the development of the Yagi antenna, which allows directional communication with electromagnetic waves. ... Year 1928 (MCMXXVIII) was a leap year starting on Sunday (link will display full calendar) of the Gregorian calendar. ...


The Yagi was first widely used during World War II for airborne radar sets, because of its simplicity and directionality. The Japanese military authorities first became aware of this technology after the Battle of Singapore when they captured the notes of a British radar technician that mentioned "yagi antenna". Japanese intelligence officers did not even recognise that Yagi was a Japanese name in this context. When "questioned" the technician said it was an antenna named after a Japanese professor. (This story is analogous to the story of American intelligence officers interrogating German rocket scientists and finding out that Robert Goddard was the real pioneer of rocket technology even though he was not well known in the US at that time.) Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... For other uses, see Radar (disambiguation). ... Combatants Malaya Command: Indian III Corps Australian 8th Div. ... Robert Goddard is the name of several notable individuals, including: Robert Goddard (scientist) (1882-1945), one of the pioneers of modern rocketry. ...


Despite its being invented in Japan, many Japanese radar engineers were unaware of the design until very late in the war, due to internal fighting between the Army and Navy. A horizontally polarized array can be seen under the left leading edge of Grumman F4F, F6F, TBF Avenger carrier based Navy aircraft. Vertically polarized arrays can be seen on the cheeks of the P-61 and on the nose cones of many WWII aircraft, notably some versions of the German Junkers Ju 88 R1 fighter-bomber, and the British Bristol Beaufighter night-fighter, and Short Sunderland flying-boat. Indeed, the latter had so many antenna elements arranged on its back it was nicknamed the "Flying Porcupine" by German airmen. In astronomy, geography, geometry and related sciences and contexts, a plane is said to be horizontal at a given point if it is locally perpendicular to the gradient of the gravity field, i. ... Grumman F4F-4 Wildcat of VF-41, circa early 1942. ... F6F Hellcat The Grumman F6F Hellcat started development as an improved F4F Wildcat, but turned into a completely new design sharing a family resemblance to the Wildcat but with no shared parts. ... Grumman TBF Avengers in 1942 The Grumman TBF Avenger (designated TBM for aircraft manufactured by General Motors) was an American torpedo bomber, developed initially for the United States Navy and Marine Corps and used by a large number of air forces around the world. ... Northrop P-61 Black Widow in flight The Northrop P-61 Black Widow was an all-metal, twin engine, twin boom, monoplane night fighter and night intruder aircraft flown by the United States Army Air Force during World War II. It was the first American aircraft designed specifically as a... A nose cone that contained one of the Voyager spacecraft is seen here as it is mounted on top of a Titan III/Centaur launch vehicle. ... The Junkers Ju 88 was a WW2 Luftwaffe twin-engine multi-role aircraft. ... The Bristol Beaufighter is also the name of a car produced by Bristol Cars in the 1980s. ... The S.25 Sunderland was a flying boat patrol bomber developed for the Royal Air Force by Short Brothers, first flown on 16 October 1937. ...


Yagi-Uda antennas are widely used by amateur radio operators worldwide for communication on frequencies from shortwave, through VHF/UHF, and into microwave bands. Hams often homebrew this type of antenna, and have provided many technical papers and software to the engineering community. Amateur radio station with modern solid-state transceiver featuring LCD and DSP capabilities Amateur radio, often called ham radio, is both a hobby and a service that uses various types of radio communications equipment to communicate with other radio amateurs for public service, recreation and self-training. ... An amateur radio operator is an individual who, typically, uses equipment at an amateur radio station to engage in two-way personal communications with other similar individuals on radio frequencies assigned to the Amateur Radio Service. ...


Wireless energy transfer

Hidetsugu Yagi attempted wireless energy transfer in February of 1926 with this antenna. Yagi and Uda published their first report on the wave projector directional antenna. Yagi managed to demonstrate a proof of concept, but the engineering problems proved to be more onerous than conventional systems. An artists depiction of a solar satellite, which could send energy wirelessly to a space vessel or planetary surface. ...


See also

A Yagi-Uda beam antenna Short Wave Curtain Antenna (Moosbrunn, Austria) A building rooftop supporting numerous dish and sectored mobile telecommunications antennas (Doncaster, Victoria, Australia) An antenna is a transducer designed to transmit or receive radio waves which are a class of electromagnetic waves. ... In geometry, the cardioid is an epicycloid which has one and only one cusp. ... The Larmor formula is used to calculate the power radiated by a nonrelativistic electron as it accelerates. ... A radio direction finder, or RDF, is a device for finding the direction to a radio source. ... Radio Direction Finding, or RDF, is the technique of locating the direction to a radio transmission. ... Little Boy was the codename of the atomic bomb which was dropped on Hiroshima, on August 6, 1945 by the 12-man crew of the B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets (Tibbets, age 92, died Nov. ...

External articles and further reading

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DENSO Corporation (株式会社デンソー) TYO: 6902 is a global automotive components manufacturer headquartered in the city of Kariya, Aichi Prefecture, Japan. ... Dai Nippon Printing ), established in 1876, is a Japanese printing company. ... Eizo Nanao Corporation ) (TYO: 6737 ), or EIZO, is a manufacturer of computer displays. ... Elpida Memory, Inc. ... Seiko Epson Corporation ), or Epson, is a Japanese company and one of the worlds largest manufacturers of inkjet, dot matrix and laser printers, scanners, desktop computers, business, multimedia and home theatre projectors, large home theatre televisions, robots and industrial automation equipment, point of sale docket printers and cash registers... FANUC Robotics America, Inc. ... Fostex is a Japanese manufacturer of loudspeakers and professional audio equipment. ... Fuji Xerox is a joint venture partnership between the Japanese photographic firm Fuji Photo Film Co. ... Fujifilm Holdings Corporation or Fujifilm ) is a Japanese company known for its photographic film and cameras. ... For the district in Saga, Japan, see Fujitsu, Saga. ... Funai Electric Co. ... It has been suggested that Hitachi Works be merged into this article or section. ... Horiba ) is a Japanese manufacturer of precision instruments for measurement and analysis. ... Hoya Corporation is a japanese company that manufacture optical products ranging from laser equipment to contact lenses. ... ICOM Incorporated ) (TYO: 6820 ) is an international manufacturer of radio transmitting and receiving equipment, founded in 1954 by Tokuzo Inoue. ... Iwatsu Electric, Co. ... A manufacturer of scanning electron microscopes, transmission electron microscopes, electron microprobes, electron beam lithography systems. ... Japan Radio Company Ltd or JRC ) TYO: 6751 is a Japanese company specialising in the field of wireless electronics for the communications industry. ... Victor Company of Japan, Limited ) (TYO: 6792 ), usually referred to as JVC, is an international consumer and professional electronics corporation based in Yokohama, Japan which was founded in 1927. ... The Kawai Musical Instruments Mfg. ... Kenwood Corporation ) (TYO: 6765 ) is a Japanese manufacturer of amateur radio as well as Hi-Fi and portable audio equipment. ... Keyence is a brand developed by Keyence Corp of Japan, with a worldwide industrial recognition. ... Konica Minolta Holdings, Inc. ... For comic book character, see Korg (comics). ... Kyocera Corporation ) (TYO: 6971 , NYSE: KYO) is a Japanese company based in Kyoto, Japan. ... Luxman is a brand name of Japanese Luxman Corporation ), a company that produces a variety of audio electronic products. ... Mabuchi Motor Company, Limited of Chiba Prefecture, Japan TYO: 6592 is the worlds number one manufacturer of small electric motors. ... This article or section does not cite its references or sources. ... Maspro Denkoh is a Japanese electronics manufacturer. ... Matsushita Electric Industrial Co. ... Hitachi Maxell ) (TYO: 6810 ), or Maxell, is a Japanese company which manufactures consumer electronics. ... Melco is a family business founded by Maketo Maki in 1975 as the company that is now known as Buffalo Inc. ... Mitsubishi Electric Corporation ) (TYO: 6503 ) is a Japanese company based in the Tokyo Building in Tokyo, manufactures electric and architectural equipment, as well as a major worldwide producer of photovoltaic panels. ... Mitsumi Electric Co. ... Nakamichi Corporate Logo Nakamichi is a historic high end audio audio company most famous for its innovative and very high quality cassette decks. ... National logo National is a brand used by Matsushita Electric Industrial Co. ... NEC Corporation (Japanese: Nippon Denki Kabushiki Gaisha; TYO: 6701 , NASDAQ: NIPNY) is a Japanese multinational IT company headquartered in Minato-ku, Tokyo, Japan. ... 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  Results from FactBites:
 
Yagi antenna (153 words)
Yagi antenna is made from the array of dipoles (elements) parallel to each other.
Yagi may be protect from weather conditions with a cylinder tube or pipe.
The Yagi-Uda antenna was invented in 1926 by Hidetsugu Yagi and Shintaro Uda in Tohoku University, Japan.
Yagi-Uda antennas (2278 words)
A Yagi-Uda antenna is familiar as the commonest kind of terrestrial TV antenna to be found on the rooftops of houses.
This is because the antenna is connected via a feeder to a transmitter whose output level may be determined in terms of the voltage at its terminals.
For moderately long Yagis with several directors, the reflector spacing and size has little effect on the forward gain, providing that there IS a reflector, but being close to the driving element it has a strong effect on the front-to-back ratio and on the driving point impedance of the antenna.
  More results at FactBites »

 
 

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