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Sector Antenna
A sector antenna is a type of directional microwave antenna with a sector-shaped radiation pattern. The word "sector" is used in the geometric sense; some portion of the circumference of a circle measured in degrees of arc. 60°, 90° and 120° designs are typical, often with a few degrees 'extra' to ensure overlap and mounted in multiples when wider or full-circle coverage is required (see photos below). The largest use of these antennas is as antennas for cell phone base-station sites. They are also used for other types of mobile communications, for example in Wi-Fi networks. They are used for limited-range distances of around 4 to 5 km. Design A typical sector antenna is depicted in the figure on the right. At the bottom, there are RF connectors for coaxial cable (feedline), and adjustment mechanisms. For its outdoor placement, the main reflector screen is produced from aluminum, and all internal parts are housed into a fiberglass radome enclosure to keep its oper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sector Antenna2
Sector may refer to: Places * Sector, West Virginia, U.S. Geometry * Circular sector, the portion of a disc enclosed by two radii and a circular arc * Hyperbolic sector, a region enclosed by two radii and a hyperbolic arc * Spherical sector, a portion of a sphere enclosed by a cone of radii from the center of the sphere Social and economic * Business sector, part of the economy which involves the trading and sale of products by companies * Economic sector, the manufacturing, finance and production of goods for consumers * Private sector, business activity created by private enterprise for profit * Public sector, delivers social services, infrastructure and institutions administered by government * Voluntary sector, a non-profit and voluntary part of an economy provided by organisations * The sector of the sector directive in government procurement in the European Union Computing * Cylinder-head-sector, an early method for giving addresses to blocks of data on a hard drive * Di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radome
A radome (a portmanteau of radar and dome) is a structural, weatherproof enclosure that protects a radar antenna (radio), antenna. The radome is constructed of material transparent to radio waves. Radomes protect the antenna from weather and conceal antenna electronic equipment from view. They also protect nearby personnel from being accidentally struck by quickly rotating antennas. Radomes can be constructed in several shapes spherical, geodesic dome, geodesic, planar, etc. depending on the particular application, using various construction materials such as fiberglass, polytetrafluoroethylene, polytetrafluoroethylene (PTFE)-coated fabric, and others. When found on fixed-wing aircraft with forward-looking radar, as are commonly used for object or weather detection, the nose cones often additionally serve as radomes. On aircraft used for airborne early warning and control (AEW&C), a rotating radome, often called a "rotodome", is mounted on the top of the fuselage for 360-degr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sector Antennas On Roof
Sector may refer to: Places * Sector, West Virginia, U.S. Geometry * Circular sector, the portion of a disc enclosed by two radii and a circular arc * Hyperbolic sector, a region enclosed by two radii and a hyperbolic arc * Spherical sector, a portion of a sphere enclosed by a cone of radii from the center of the sphere Social and economic * Business sector, part of the economy which involves the trading and sale of products by companies * Economic sector, the manufacturing, finance and production of goods for consumers * Private sector, business activity created by private enterprise for profit * Public sector, delivers social services, infrastructure and institutions administered by government * Voluntary sector, a non-profit and voluntary part of an economy provided by organisations * The sector of the sector directive in government procurement in the European Union Computing * Cylinder-head-sector, an early method for giving addresses to blocks of data on a hard drive * Di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmitting Tower Top Us
In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna (radio), antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the Antenna (radio), antenna. When excited by this alternating current, the antenna radiates radio waves. Transmitters are necessary component parts of all electronic devices that communicate by radio communication, radio, such as radio broadcasting, radio and television broadcasting stations, cell phones, walkie-talkies, Wireless LAN, wireless computer networks, Bluetooth enabled devices, garage door openers, two-way radios in aircraft, ships, spacecraft, radar sets and navigational beacons. The term ''transmitter'' is usually limited to equipment that generates radio waves for Communication engineering, communication purposes; or radiolocation, such as radar and navigational transmitters. Generators of radio waves for heatin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sector Antennas On Mast
Sector may refer to: Places * Sector, West Virginia, U.S. Geometry * Circular sector, the portion of a disc enclosed by two radii and a circular arc * Hyperbolic sector, a region enclosed by two radii and a hyperbolic arc * Spherical sector, a portion of a sphere enclosed by a cone of radii from the center of the sphere Social and economic * Business sector, part of the economy which involves the trading and sale of products by companies * Economic sector, the manufacturing, finance and production of goods for consumers * Private sector, business activity created by private enterprise for profit * Public sector, delivers social services, infrastructure and institutions administered by government * Voluntary sector, a non-profit and voluntary part of an economy provided by organisations * The sector of the sector directive in government procurement in the European Union Computing * Cylinder-head-sector, an early method for giving addresses to blocks of data on a hard drive * Di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Remote Control
In electronics, a remote control (also known as a remote or clicker) is an electronic device used to operate another device from a distance, usually wirelessly. In consumer electronics, a remote control can be used to operate devices such as a television set, DVD player or other home appliance. A remote control can allow operation of devices that are out of convenient reach for direct operation of controls. They function best when used from a short distance. This is primarily a convenience feature for the user. In some cases, remote controls allow a person to operate a device that they otherwise would not be able to reach, as when a garage door opener is triggered from outside. Early television remote controls (1956–1977) used ultrasonic tones. Present-day remote controls are commonly consumer infrared devices which send digitally-coded pulses of infrared radiation. They control functions such as power, volume, channels, playback, track change, heat, fan speed, and vario ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phase Shifter
A phase shift module is a microwave network module which provides a controllable phase shift of the RF signal. Phase shifters are used in phased arrays. Classification Active versus passive Active phase shifters provide gain, while passive phase shifters are lossy. * Active: ** Applications: active electronically scanned array (AESA), passive electronically scanned array (PESA) ** Gain: The phase shifter amplifies while phase shifting ** Noise figure (NF) ** Reciprocity: not reciprocal * Passive: ** Applications: active electronically scanned array (AESA), passive electronically scanned array (PESA) ** Loss: the phase shifter attenuates while phase shifting ** NF: NF = loss ** Reciprocity: reciprocal Analog versus digital * Analog phase shifters provide a continuously variable phase shift or time delay. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Broadcast Range
A broadcast range (also listening range or listening area for radio, or viewing range or viewing area for television) is the service area that a broadcast station or other transmission covers via radio waves (or possibly infrared light, which is closely related). It is generally the area in which a station's signal strength is sufficient for most receivers to decode it. However, this also depends on interference from other stations. Legal definitions The "primary service area" is the area served by a station's strongest signal. The "city-grade contour" is 70 dBμ (decibels relative to one microvolt per meter of signal strength) or 3.16mV/m (millivolts per meter) for FM stations in the United States, according to Federal Communications Commission (FCC) regulations. This is also significant in broadcast law, in that a station must cover its city of license within this area, except for non-commercial educational and low-power stations. The legally protected range of a stat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RF Interference
Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data. Both man-made and natural sources generate changing electrical currents and voltages that can cause EMI: ignition systems, cellular network of mobile phones, lightning, solar flares, and auroras (northern/southern lights). EMI frequently affects AM radios. It can also affect mobile phones, FM radios, and televisions, as well as observations for radio astronomy and atmospheric science. EMI can be used intentionally for radio jamming, as in electronic warfare. History Since the earliest days of radio c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beam Tilt
Beam tilt is used in radio to aim the main lobe of the vertical plane radiation pattern of an antenna below (or above) the horizontal plane. The simplest way is mechanical beam tilt, where the antenna is physically mounted in such a manner as to lower the angle of the signal on one side. However, this also raises it on the other side, making it useful in only very limited situations. More common is electrical beam tilt, where the phasing between antenna elements is tweaked to make the signal go down (usually) in all directions. This is extremely useful when the antenna is at a very high point, and the edge of the signal is likely to miss the target (broadcast audience, cellphone users, etc.) entirely. With electrical tilting, front and back lobes tilt in the same direction. For example, an electrical downtilt will make both the front lobe and the back lobe tilt down. This is the property used in the above example where the signal is pointed down in all directions. On th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line-of-sight Propagation
Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves travel in a direct path from the source to the receiver. Electromagnetic transmission includes light emissions traveling in a straight line. The rays or waves may be diffracted, refracted, reflected, or absorbed by the atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles. In contrast to line-of-sight propagation, at low frequency (below approximately 3 MHz) due to diffraction, radio waves can travel as ground waves, which follow the contour of the Earth. This enables AM radio stations to transmit beyond the horizon. Additionally, frequencies in the shortwave bands between approximately 1 and 30 MHz, can be refracted back to Earth by the ionosphere, called skywave or "skip" propagation, thus giving radio transmissions in this range a potentially global reach. However, at frequencies above ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commercial Broadcasting
Commercial broadcasting (also called private broadcasting) is the broadcasting of television programs and radio programming by privately owned corporate media, as opposed to state sponsorship. It was the United States′ first model of radio (and later television) during the 1920s, in contrast with the public television model in Europe during the 1930s, 1940s and 1950s, which prevailed worldwide, except in the United States and Brazil, until the 1980s. Features Advertising Commercial broadcasting is primarily based on the practice of airing radio advertisements and television advertisements for profit. This is in contrast to public broadcasting, which receives government subsidies and usually does not have paid advertising interrupting the show. During pledge drives, some public broadcasters will interrupt shows to ask for donations. In the United States, non-commercial educational (NCE) television and radio exists in the form of community radio; however, premium cable servi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
