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Monopole antenna - Wafer Butterfly Valve Manufacturer - China Butterfly Valve Manufacturer by ewrt wrtgnfh
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Monopole antenna - Wafer Butterfly Valve Manufacturer - China Butterfly Valve Manufacturer by EWRT WRTGNFH
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| Article Posted: 12/28/2010 |
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Monopole antenna - Wafer Butterfly Valve Manufacturer - China Butterfly Valve Manufacturer |
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Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2006) Monopole antenna used for broadcasting A monopole antenna is a type of radio antenna formed by replacing one half of a dipole antenna with a ground plane at right-angles to the remaining half. If the ground plane is large enough, the monopole behaves like a dipole, as if its reflection in the ground plane formed the missing half of the dipole, except that the radiation from the reflected half is added to that of the real half (see image antenna). However, a monopole will have a directive gain of 5.19dB (gain is twice (3dB over) that for a half-wave dipole antenna), and a lower input resistance. Monopoles may be used from a few hundred kHz (navigation beacons and broadcast stations) through several GHz in frequency and are commonly one-quarter of a wavelength long, but may be shorter or longer. When used for radio broadcasting, the radio frequency power from the broadcasting transmitter is fed across the base insulator between the tower and a ground system. The ideal ground system for AM broadcasters comprises at least 120 buried copper or phosphor bronze radial wires at least one-quarter wavelength long and a ground-screen in the immediate vicinity of the tower. All the ground system components are bonded together, usually by welding, brazing or using coin silver solder to help reduce corrosion. Monopole antennas that use guy-wires for support are called masts in some countries. In the United States, the term ast is generally used to describe a pipe supporting a smaller antenna, so both self-supporting and guy-wire supported radio antennas are simply called monopoles if they stand alone. If multiple monopole antennas are used in order to control the direction of Radio Frequency (RF) propagation, they are called directional antenna arrays. The RF feed-point impedance across this antenna base insulator is well defined and is approximately as shown in the chart. Approximate feed-point impedance In the United States, the Federal Communications Commission (FCC) requires that the transmitter power input to the antenna be measured and maintained. The power input is calculated as the square of the measured current, i, flowing into the antenna from the transmission line multiplied by the real part of the antenna's feed-point impedance, r. P = i2r This impedance is periodically measured to verify the stability of the antenna and ground system. Normally, an impedance matching network matches the impedance of the antenna to the impedance of the transmission line feeding it. Examples of monopole antennas are: the whip antenna the radio mast (when isolated from the ground and bottom-fed) Monopole antenna's have become one of the mainstay components of mobile and internet networks across the globe. Their relative low cost and fast installation makes them an obvious choice for developing countries. See also Cellular repeater Signal strength Folded unipole antenna Rubber Ducky antenna Electrical lengthening External links Errante's virtual ground monopole antenna www.Radiondistics.com Radiation of a quarter wavelength monopole v d e Antenna types Isotropic Isotropic radiator Helical antenna Omnidirectional Dipole antenna Monopole antenna Whip antenna Random wire antenna Directional Beverage antenna Horizontal curtain Horn Log-periodic antenna Phased array Parabolic antenna Loop antenna Regenerative loop antenna Rhombic antenna Yagi antenna Application-specific ALLISS Categories: Radio frequency antenna typesHidden categories: Articles lacking sources from December 2006 All articles lacking sources We are high quality suppliers, our products such as Wafer Butterfly Valve Manufacturer , China Butterfly Valve Manufacturer for oversee buyer. To know more, please visits Pvc Butterfly Valve.
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