Unreferenced date December 2009 Image LPDA large.jpg thumb right Log periodic dipole array A directionalantenna or beam antenna is an antenna electronics antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced Interference communication interference from unwanted sources. Directional antennas like Yagi Uda antenna s provide increased performance over dipole antenna s when a greater concentration of radiation in a certain direction is desired. All practical antennas are at least somewhat directional, although usually only the direction in the plane parallel to the earth is considered, and practical antennas can easily be omnidirectional antenna omnidirectional in one plane. The most common types are the Yagi Uda antenna , the log periodic antenna , and the corner reflector , which are frequently combined and commercially sold as residential TV antenna s. Cellular repeater s often make use of external directional antennas to give a far greater signal than can be obtained on a standard cell phone . Satellite Television receivers usually use parabolic antenna s. For long and medium wavelength frequencies , tower array s are used in most cases as directional antennas. See also Amateur radio direction finding Cantenna Cardioid Cassegrain antenna Cassegrain reflector Antenna gain High gain antenna Loop antenna Omnidirectional antenna Parabolic antenna Radio direction finder Radio propagation model , Antenna subsection References Reflist Antenna Types DEFAULTSORT DirectionalAntenna Category Radio frequency antenna types de Richtantenne es Antena direccional lt Kryptin antena pl Antena kierunkowa ... more details
antenna , a simple antenna usually constructed from two wires in opposite phases placed end to end Directionalantenna , or beam antenna, radiates greater power primarily in one direction Horn antenna , a type of directionalantenna shaped like a horn Metamaterial antenna , a class of antenna incorporating metamaterials to increase performance of a miniaturized electrically small antenna systems Omnidirectional antenna , an antenna system which radiates power uniformly in all directions in one plane Parabolic antenna , an antenna shaped like a parabola in one or both planes Biology Antenna biology ...style float right wiktionary antenna Tocright Antenna pl. antennas in radio TV, antennae in biology may refer to Science and engineering Antenna radio , also known as an aerial, a transducer designed to transmit or receive electromagnetic e.g. TV or radio waves Television antenna or TV aerial , is an antenna ... of two colliding galaxies NGC 4038 and NGC 4039 Technology Antenna tower , a tall designed ... present in most cell types of eukaryotes Antenna journal , the journal of the Royal Entomological Society Entertainment Antenna band , an American indie rock band active from 1991 to 1994, formed in Bloomington ... by Isabelle Antena a pseudonym for Isabelle Powaga . Antenna Cave In album Antenna Cave In album , the third studio album and first major label album by American rock band Cave In, released in 2003 Antenna GO GO 7188 album Antenna GO GO 7188 album , the seventh studio album by Japanese rock band GO GO 7188, released in 2009 Antenna ZZ Top album Antenna ZZ Top album , the eleventh studio album by American blues rock band ZZ Top, released in 1994 Antenna film Antenna film , a satirical 1969 Dutch film directed by Adriaan Ditvoorst Antenna , an episode of the Adult Swim animated television series ... terrestrial television channel Antenna TV , a U.S. television channel established in 2011 ... radio station RDP Antena 3 , Portuguese public radio station See also Aerial disambiguation Antenna ... more details
Unreferenced date January 2007 In broadcast engineering , directional array refers to an Antenna array electromagnetic antenna array arranged such that the Superposition principle superposition of the electromagnetic wave s produce a predictable electromagnetic field . By spacing 2 or more antenna elements apart, changing the length of the transmission line from the transmitter , varying the power output, and shifting the Phase waves phase , radio Broadcasting broadcasters can shape the area of signal coverage. Geographically close Co channel interference co channel or adjacent channel stations employ directional arrays or a single directionalantenna so that other broadcasters may utilize the same or adjacent frequency . In the United States , the Federal Communications Commission offers a first come, first served approach, meaning licenses granted on co channel or adjacent channels must protect the service contour of the previously licensed facility, thus, a directional array may be used to shape the station around existing facilities. DEFAULTSORT Directional Array Category Broadcast engineering Category Radio frequency antenna types pl Szyki kierunkowe Telecomm stub ... more details
Directional light may refer to Shading Light sources Headlamp Directional headlamps Light beam Light tube See also Direction disambiguation Light disambiguation dab ... more details
Bi directional may refer to Bi directional text Two way communication Bi directional railway signalling Bi directional vehicle a locomotive, railcar or tram streetcar with controls at each end Short pages monitor This long comment was added to the page to prevent it being listed on Special Shortpages. It and the accompanying monitoring template were generated via Template Longcomment. Please do not remove the monitor template without removing the comment as well. disambig ... more details
Dicdef Image True vertical depth.jpg thumb 250 px right Depiction of a directional well. br Line a is an imaginary line representing the True vertical depth , while line b is the borehole itself, and its length is called the measured depth A directional well , as it is known in the oil industry , is an oil well with a borehole that deviates from a vertically straight line. This is normally an intentional decision and done purposefully, to hit several target sands, for instance. References http www.glossary.oilfield.slb.com Display.cfm?Term directional 20well Directional well , Oilfield Glossary , Schlumberger Petroleum stub Category Petroleum engineering Category Oilfield terminology Category Drilling technology ... more details
Context date October 2009 Directional symmetry is roughly defined as things going the same direction, and is to be distinguished from directional asymmetry , meaning things going different directions. The following formula tests for directional symmetry If math t , math is the actual signal and math hat t math is the predicted one we have br math operatorname DS t, hat t frac 100 n 1 sum i 2 n 1 d i math , math d i begin cases 1, & mbox if t i t i 1 hat t i hat t i 1 ge 0 0, & mbox otherwise end cases math External links http spiedl.aip.org getabs servlet GetabsServlet?prog normal&id OPEGAR000038000012002114000001&idtype cvips&gifs yes Directional symmetry transform for human face location DEFAULTSORT Directional Symmetry Category Symmetry Category Signal processing geometry stub ... more details
Multiple issues unreferenced November 2006 cleanup Jan 2011 Directional arrows are a type of traffic sign directing people to points of interest such as commuter rail stations, colleges , tourist attractions, neighboring communities and the like, but the popularity of these signs is falling because of the use of websites on which to look up driving directions such as Mapquest . Clarify date September 2011 Citation needed date September 2011 DEFAULTSORT Directional Arrow Category Traffic signs planning stub ... more details
In telecommunication s and radar engineering, antenna boresight is the axis of maximum antenna gain gain maximum radiated power of a DirectionalantennadirectionalAntenna radio antenna . For most antennas the boresight is the axis of symmetry of the antenna. For example, for axial fed dish antenna s, the antenna boresight is the axis of symmetry of the parabolic dish, and the antenna radiation pattern the main lobe is symmetrical about the boresight axis. Most antennas boresight axis is fixed by their shape and cannot be changed. However phased array antenna s can electronically steer the beam, changing the angle of the boresight by shifting the relative phase of the radio waves emitted by different antenna elements, and even radiate beams in multiple directions multiple boresights . ref http www.ccrs.nrcan.gc.ca glossary index e.php?id 3158 ref The term boresight came from high gain antenna s such as parabolic dishes, which produce narrow, pencil shaped beams which are difficult to aim accurately at a distant receiving antenna. These often are equipped with optical boresight firearm boresight s to assist in aiming. References reflist Category Antennas radio telecomm stub ... more details
File Directional solidification.svg thumb 300px Directional solidification File Progressive solidification.svg thumb 300px Progressive solidification Directional solidification and progressive solidification describe types of solidification within casting s. Directional solidification describes solidification that occurs from farthest end of the casting and works its way towards the sprue manufacturing sprue . Progressive solidification, also known as parallel solidification , ref name stefanescu67 harvnb Stefanescu 2008 p 67 . ref is solidification that starts at the walls of the casting and progresses perpendicularly from that surface. ref name chastain104 harvnb Chastain 2004 p 104 . ref Theory Most metal s and alloys shrinkage casting shrink as the material changes from a liquid state to a solid state. Therefore, if liquid material is not available to compensate for this shrinkage a shrinkage defect forms. When progressive solidification dominates over directional solidification a shrinkage defect will form. ref name chastain104 File Casting solidification conditions.svg thumb left 300px The geometrical shape of the mold cavity has direct effect on progressive and directional solidification. At the end of tunnel type geometries divergent heat flow occurs, which causes that area of the casting to cool faster than surrounding areas this is called an end effect . Large cavities do not cool as quickly as surrounding areas because there is less heat flow this is called a riser ... areas. ref name stefanescu68 harvnb Stefanescu 2008 p 68 . ref In order to induce directional solidification ..., and pouring temperature can be utilized. ref harvnb Chastain 2004 pp 104 105 . ref Directional solidification ... of the metal can be scrapped or recycled. The suitability of directional solidification in removing ... in question, as described by the Scheil equation . Directional solidification is frequently employed ... Butterworth Heinemann edition 2nd isbn 0750647906 . Citation last Wlodawer first Robert title Directional ... more details
dicdef Unidirectional refers to an object that moves in only one direction at one time. It can refer to In communications theory, it is referred to as simplex communication or using ITU standards it refers to half duplex signaling behavior. In Transportation a uni directional tram or railcar is a tram or railcar with controls at one end only. disambig ... more details
impact on the surrounding area. Directional boring is used when trenching or excavating is not practical ... , Ductile iron , and steel if the pipes can be pulled through the drilled hole. Directional .... Equipment The equipment used in a horizontal directional drilling depends on the outter diameter ..., directional drills equipped with as much as 100,000 pounds or more of thrust pullback is used ... fluid to the drillstem. Directional drilling stem is made from heat treated high carbon steel for strength ... foot lengths and have male threading on one end, and female on the other. It is common for a directional ... equipment is needed to assist directional drilling or HDD to work smoothly, such as drilling mud recycling system , shale shaker , mud cleaner, centrifugal pump, mud tank s, etc. Technique Directional ..., no access pit, shorter completion times, directional capabilities, and environmental safety. The technique ... the reamer to allow centering of the pipe in the newly reamed path. Horizontal directional drilling ... by directional boring Location and guidance of the drilling is an important part of the drilling ... 2005 . Horizontal Directional Drilling , p. 1 263. Mcgraw Hill, New York. ISBN 007145473X. Short, Jim 1993 . Introduction to Directional and Horizontal Drilling , p. 1 222. PennWell Books ... of Horizontal Directional Drilling, Brisbane 2006. External links http www.directionalboringcentral.com library dba dbapamphlet.htm The Directional Boring Advantage describes techniques used, with diagrams. DEFAULTSORT Directional Boring Category Subterranea geography Category Drilling technology Category Trenchless technology de Horizontalsp lbohrverfahren it Directional drilling he ... more details
loudspeaker is naturally more directional because of its large size, a source with equivalent directivity .... The larger the speaker array, the more directional, and the smaller the size of the speaker array, the less directional it is. This is fundamental physics, and cannot be bypassed, even by using phased ... of large speaker panels, such as electrostatic loudspeakers , tend to be more directional than small speakers, for the same reasons as above they are somewhat more directional only because they tend to be physically ... the size of a small traditional speaker would be non directional. The directivity for various source ... DEFAULTSORT Directional Sound Category Sound Category Acoustics Category Ultrasound sv Riktat ljud ... more details
directional drill in operation File Reservoir modeling software screen snapshot of isopach map ... reservoir could use Directional drilling to accurately target the 28 ft thick space, 8,500ft underground ... and Oil reservoir . Directional drilling or slant drilling is the practice of drilling non vertical oil well well s. It can be broken down into three main groups Oilfield Directional Drilling, Utility Installation Directional Drilling or H.D.D. or Horizontal Directional Drilling Directional boring , and SIS ... survey tools were developed by Robert Richardson, an independent directional driller who first ... . Counter experience had also given early directional drillers DD s principles of BHA design and drilling ... Beach, California , became a pioneer in directional drilling when he and George Failing of Enid ... the world s largest directional company in 1973. Combined, these survey tools and BHA designs made directional ..., which allows tools down hole to send directional data back to the surface without disturbing drilling operations , directional drilling became easier. Certain profiles could not be drilled without the drill ... direction while rotating is desirable. Several companies have developed tools which allow directional ... technology has allowed access to and or directional control in previously inaccessable or uncontrollable ... and is considered the Grandfather of RSS technology. In 2010 he became the first BHI directional driller ... wellbore to suppress the high pressure in the original wellbore causing the blowout. Most directional ... the drilling commences. When the directional driller starts the drilling process, periodic surveys .... ref Cite web url http chinookconsulting.ca News Directional drilling glossary.html title Glossary ..., directional drilling and horizontal drilling was much slower than vertical drilling due to the need ... and rounded See also Devico AS Directional boring Geosteering Hydraulic fracturing Logging ... category Petroleum industry Shale gas technology yes DEFAULTSORT Directional drilling Category Drilling ... more details
In mathematics , the directional derivative of a multivariate differentiable function along a given vector mathematics vector V at a given point P intuitively represents the instantaneous rate of change of the function, moving through P in the direction of V . It therefore generalizes the notion of a partial derivative , in which the direction is always taken parallel to one of the coordinate axes . The directional derivative is a special case of the G teaux derivative . Definition The directional derivative of a scalar function math f bold x f x 1, x 2, ldots, x n math along a unit vector math ... at x , then the directional derivative exists along any unit vector u , and one has math ... the gradient and math cdot math is the Dot product Euclidean inner product . At any point x , the directional ... math bold u math at the point x . One sometimes permits non unit vectors, allowing the directional ... is expected to be a vector space. Notation Directional derivatives can be also denoted by math nabla ... derivative hold for the directional derivative. These include, for any functions f and g defined in a neighborhood ... nabla v g p math li ol In differential geometry seealso Tangent space Tangent vectors as directional ... at p , then the directional derivative of f along v , denoted variously as math nabla v f p math ... 0 p and &prime 0 v . Then the directional derivative is defined by math nabla v f p left. frac ... derivative is a directional derivative taken in the direction normal that is, orthogonal to some surface ... for example Neumann boundary condition . If the normal direction is denoted by math bold n math , then the directional ... and T. J. R. Hughes, 2000, Mathematical Foundations of Elasticity , Dover. ref The directional directive provides a systematic way of finding these derivatives. The definitions of directional derivatives ... links http mathworld.wolfram.com DirectionalDerivative.html Directional derivatives at MathWorld http planetmath.org encyclopedia PartialDerivativeWithRespectToAVector.html Directional derivative ... more details
Directional statistics is the subdiscipline of statistics that deals with directions unit vector s in R sup n sup , Cartesian Coordinate System axes lines through the origin in R sup n sup or rotation s in R sup n sup . More generally, directional statistics deals with observations on compact Riemannian manifold s. Image Fb5 cover.jpg thumb 250px right The overall shape of a protein can be parameterized as a sequence of points on the unit sphere . Shown are two views of the spherical histogram of such points for a large collection of protein structures. The statistical treatment of such data is in the realm of directional statistics. ref cite web url http compbiol.plosjournals.org perlserv ?request get document&doi 10.1371 journal.pcbi.0020131 title Hamelryck, T., Kent, J., Krogh, A. 2006 Sampling realistic protein conformations using local structural bias. PLoS Comput. Biol., 2 9 e131 accessdate 2008 02 01 publisher Public Library of Science PLoS ref The fact that 0 degree angle degrees ... be regarded as directional include statistics involving temporal periods e.g. time of day, week .... ref Bahlmann, C., 2006 , Directional features in online handwriting recognition, Pattern Recognition ... 5 circ. math This may be more succinctly stated by realizing that directional data are in fact vectors ... Central limit theorem for directional statistics . It can be shown ref name SRJ cite book title Topics ... directional statistics. http www.kovcomp.com oriana Oriana , Windows software for directional statistics. See also Yamartino method Wrapped distribution References references Books on directional ... University Press, 1993. ISBN 0 521 45699 1 Mardia, KV. and Jupp P., Directional Statistics 2nd edition ... 2008 11 25 directional statistics.pdf Directional Statistics , Concepts and Techniques in Modern Geography ... directional Category Statistical data types Category Statistical models Category Types of probability distributions Category Directional statistics ja fr Statistiques directionnelles ... more details
Technical date April 2011 Directional stability is stability of a moving body or vehicle about an axis which is perpendicular to its direction of motion. Stability of a vehicle concerns itself with the tendency of a vehicle to return to its original direction in relation to the oncoming medium water, air, road surface, etc. when disturbed rotated away from that original direction. If a vehicle is directionally stable, a restoring torque moment is produced which is in a direction opposite to the rotational disturbance. This pushes the vehicle in rotation so as to return it to the original orientation, thus tending to keep the vehicle oriented in the original direction. Directional stability is frequently called weather vaning because a directionally stable vehicle free to rotate about its center of mass is similar to a weather vane rotating about its vertical pivot. With the exception of spacecraft, vehicles generally have a recognisable front and rear and are designed so that the front points more or less in the direction of motion. Without this stability, they may tumble end over end, spin or orient themselves at a high angle of attack , even broadside on to the direction of motion. At high angles of attack, Drag coefficient drag force s may become excessive, the vehicle may be impossible to control, or may even experience structural failure. In general, land, sea, air and underwater vehicles are designed to have a natural tendency to point in the direction of motion. Example Road Vehicle Arrows, darts, rockets and airships have tail surfaces to achieve stability. A road vehicle does not have elements specifically designed to maintain stability, but relies primarily on the distribution ..., moment of inertia and speed, so the damping is positive, and the directional motion should .... It follows that the condition of the rear tyres is more critical to directional stability ... weight production vehicle designed around a small engine increases both its directional stability ... more details
File Aerial antenna.JPG thumb right 250px A multiband US television reception antennaAntenna array may refer to Antenna array electromagnetic a group of isotropic radiators such that the currents running through them are of different amplitudes and phases Interferometry Interferometric array of radio telescopes used in radio astronomy Phased array , also known as a smart antenna , an electronically steerable directionalantenna typically used in Radar and in wireless communication systems, in view to achieve beamforming , multiple input and multiple output MIMO communication or space time coding Directional array refers to multiple antennas arranged such that the superposition of the electromagnetic waves produce a predictable electromagnetic field. Direction finding Watson Watt .2F Adcock antenna array Watson Watt Adcock antenna array the Watson Watt technique uses two Adcock antenna pairs to perform an amplitude comparison on the incoming signal. References reflist disambig ... more details
Image SatelliteAntenna 137MHz.jpg thumb right A turnstile antenna for Low Earth Orbit LEO weather satellites . A turnstile antenna is a set of two dipole antenna s aligned at right angles to each other and fed 90 degrees out of phase. The name reflects that the antenna looks like a turnstile when mounted horizontally. When mounted horizontally the antenna is nearly omnidirectional on the horizontal plane. When mounted vertically the antenna is directional to a right angle to its plane and is circularly polarized . The turnstile antenna is often used for communication satellite s because, being circularly polarized, the polarization of the signal doesn t rotate when the satellite rotates. The principles of the turnstile antenna are also applicable to Yagi antenna Yagi and Log periodic antenna s. External links http www.mikestechblog.com joomla ham radio ham radio antennas category 65 2 meter turnstile antenna for amateur satellite communications.html Turnstile Construction plans for satellite communication http www.west.net jay turnstile.html Construction plans http www.digitalham.co.uk weather equipment turnstile antenna Turnstile design for APT weather satellite reception Antenna Types radio comm stub mast stub Category Radio frequency antenna types de Kreuzdipol sv V ndkorsantenn it Antenna turnstile ... more details
Unreferenced date December 2009 File Vu2gmn antenna.jpg thumb right 300px An antenna rotator unit is visible in the middle of the mast. An Antenna radio antenna rotator is a device which is used to change the orientation of a directionalantenna . Most antenna rotators have two parts, the rotator unit and the controller. The controller is normally placed near the equipment which the antenna is connected to, while the rotator is mounted on the antenna mast directly below the antenna. Rotators are commonly used in amateur radio and military communications installations. They are also used with TV and FM broadcasting FM antennas, where stations are available from multiple directions, as the cost of a rotator is significantly less than that of installing a second antenna to receive stations from multiple directions. Rotators are manufactured for different sizes of antennas and installations. For example, a consumer TV antenna rotator has enough power to turn a TV FM or small Ham antenna. These units typically cost around US 70. Heavy duty Ham rotators are designed to turn extremely large, heavy, high frequency shortwave beam antennas, but cost hundreds and possibly thousands of dollars. DEFAULTSORT Antenna Rotator Category Antennas Mast stub ... more details
Multiple issues unreferenced January 2010 cleanup January 2010 orphan May 2010 A Zarya Antenna is a special type of directional mediumwave broadcasting Antenna radio antenna consisting of a long straight row of grounded lattice tower s with a height of approximate 50 metres in a distance of 100 metres. These towers carry the antenna wire. Three types of Zarya antennas, which exist at most larger AM broadcasting facilities in former Soviet Union, are used. They use some configuration but different length values, which are 1500, 2500 and 3500 metres. External links http www.radioscanner.ru forum topic30777 4.html Category Communications in Russia de Sarja Antenne ... more details
File Slot antenna section3.jpg thumb right 250px Cross section of a slotted waveguide antenna from a marine radar set. A slot antenna consists of a metal surface, usually a flat plate, with a hole or slot cut out. When the plate is driven element driven as an antenna radio antenna by a driving frequency, the slot radiates electromagnetic wave s in similar way to a dipole antenna . The shape and size of the slot, as well as the driving frequency, determine the radiation pattern radiation distribution pattern . Often the radio waves are provided by a waveguide , and the antenna consists of slots in the waveguide. Slot antennas are often used at Ultrahigh frequency UHF and microwave frequencies instead of line antennas when greater control of the radiation pattern is required. Slot antennas are widely used in radar antennas, for the sector antenna s used for cell site cell phone base stations , and are often found in standard desktop microwave sources used for research purposes. A slot antenna s main advantages are its size, design simplicity, robustness, and convenient adaptation to mass production using PC board technology. The slot antenna was invented in 1938 by Alan Blumlein , while working for EMI . He invented it in order to produce a practical type of antenna for VHF television broadcasting that would have horizontal polarization, an omni directional horizontal radiation pattern and a narrow vertical radiation pattern. ref citation first Alan last Blumlein title Improvements in or relating to high frequency electrical conductors or radiators work British patent no. 515684 date 1938 03 07 ref ref cite book title The life and times of A D Blumlein first Russell last Burns publisher Institution of Engineering and Technology year 2000 ISBN 0 85296 773 X ref References reflist See also Slotted waveguide External links http www.antenna theory.com antennas aperture slot.php Slot Antennas www.antenna theory.com Antenna Types Category Radio frequency antenna types tech stub ... more details
VHF UHF biconical antenna 170 1100 MHz with omni directional H plane pattern Image Vpol dual band blade antenna blade L1 3D.jpg thumb Radiation pattern of a 3 2 monopole antenna. Although the radiation ... HPBW 2 right dB math See also Choke ring antennaDirectionalantenna References Reflist Category ...Image L over2 rad pat per.jpg thumb The radiation pattern of a simple omnidirectional antenna, a vertical half wave dipole antenna . In this graph the antenna is at the center of the donut . Radial distance ... in horizontal directions, dropping to zero directly above and below the antenna. In radio communication , an omnidirectional antenna is an antenna electronics antenna which radiates radio wave power ... or below the plane, dropping to zero on the antenna s axis. This radiation pattern is often described as doughnut shaped . Note that this is different from an isotropic radiator isotropic antenna ... antennas are the whip antenna , Rubber Ducky antenna Rubber Ducky , Monopole antenna ground plane antenna , vertically oriented dipole antenna , discone antenna , mast radiator , horizontal loop antenna sometimes known colloquially as a circular aerial because of the shape , and the halo antenna . Higher gain omnidirectional antennas can also be built. Higher gain in this case means that the antenna ... the current in each dipole is in phase. ref cite book editor Johnson, R, Jasik, H title Antenna ... or COCO antenna uses transposed coaxial sections to produce in phase half wavelength radiators ... antennas are the coaxial collinear COCO antenna ref cite journal doi 10.1109 8.18724 author Judasz, T., Balsley, B. title Improved Theoretical and Experimental Models for the Coaxial Colinear Antenna ... 1989 ref and Omnidirectional Microstrip antenna Microstrip Antenna OMA . ref cite journal doi 10.1002 mop.21187 author Bancroft R title Design Parameters of an Omnidirectional Planar Microstrip Antenna .... ref cite web author Yanaga Kurashima Arita Kobayashi title A Planar UWB Monopole Antenna Formed on a Printed ... more details
File Halo antenna diagram.png thumb 320 px A gamma matched halo A halo antenna , or halo , is a horizontally polarized, omni directional 1 2 wavelength dipole Antenna radio antenna . It is shaped like a loop with a small break on the side of the loop directly opposite the feedpoint, so that the dipole ends do not meet. The antenna is usually one continuous conductor, fed with a gamma match capacitor, although a double halo system may be utilized, with a larger radiating loop at the top, and a smaller loop on the bottom that is fed directly. ref Stites, Francis H. October 1947 . A Halo for Six Meters . QST, p. 24. ref The double loop system was the feeding method described in the original patent, with the gamma match feed being more predominate with modern halos. The effective difference is that the double loop is balanced, while a gamma match is unbalanced. The halo antenna is distinct from the Loop antenna Small loops magnetic loop antenna , which is similar, but quite a bit smaller, and the full wave loop antenna loop , which is larger and in which the element is a complete loop. Advantages of a halo antenna When constructed correctly, the antenna will present a good match to 50 ohm coax with a low Standing wave ratio SWR . The antenna provides a low angle omni directional pattern. The radiating element of the halo is Ground electricity grounded , which tends to reduce static buildup, an advantage shared by many antennas fed with a gamma match. The physical diameter of a halo is small enough to be effectively used as a mobile antenna on the higher vhf bands and above. Halos ... pattern. Disadvantages of a halo antenna Due to their narrow pattern, halo antennas perform ... High Frequency Antenna System country code US description patent number 2324462 External links http www.kr1st.com 2mhalo.htm www.kr1st.com 2mhalo Construct a halo antenna for two meters. http fedler.com ... Halo Antenna Category Articles created via the Article Wizard Category Antennas radio ... more details
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