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Rhombic Antenna
A rhombic antenna is made of four sections of wire suspended parallel to the ground in a diamond or "rhombus" shape. Each of the four sides is the same length – about a quarter-wavelength to one wavelength per section – converging but not touching at an angle of about 42° at the fed end and at the far end. The length is not critical, typically from one to two wavelengths ( λ), but there is an optimum angle for any given length and frequency. A horizontal rhombic antenna radiates horizontally polarized radio waves at a low elevation angle off the pointy ends of the antenna. If the sections are joined by a resistor at either of the acute (pointy) ends, then the antenna will receive from and transmit to only the direction the end with the resistor points at. Its principal advantages over other types of antenna are its simplicity, high forward gain, wide bandwidth, and the ability to operate over a wide range of frequencies. Description A rhombic antenna consists of one t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhombic UHF TV Antenna
Rhombic may refer to: *Rhombus, a quadrilateral whose four sides all have the same length (often called a diamond) *Rhombic antenna, a broadband directional antenna most commonly used on shortwave frequencies * polyhedra formed from rhombuses, such as the rhombic dodecahedron or the rhombic triacontahedron or the rhombic dodecahedral honeycomb or the rhombic icosahedron or the rhombic hexecontahedron or the rhombic enneacontahedron or the trapezo-rhombic dodecahedron * other things that exhibit the shape of a rhombus, such as rhombic tiling, Rhombic Chess, rhombic drive, Rhombic Skaapsteker, rhombic egg eater, rhombic night adder, forest rhombic night adder {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ionosphere
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on Earth. Travel through this layer also impacts GPS signals, resulting in effects such as deflection in their path and delay in the arrival of the signal. History of discovery As early as 1839, the German mathematician and physicist Carl Friedrich Gauss postulated that an electrically conducting region of the atmosphere could account for observed variations of Earth's magnetic field. Sixty years later, Guglielmo Marconi received the first trans-Atlantic radio signal on December 12, 1901, in St. John's, Newfoundland (now in Canada) usin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crowsley Park
Crowsley Park is a country estate in South Oxfordshire, central-southern England, owned by the British Broadcasting Corporation (BBC). Overview Since the Second World War, Crowsley Park has been the site of a signals-receiving station used by BBC Monitoring, based until May 2018 at Caversham Park, three miles to the south. The Crowsley receiving facility is now an outstation of BBC Monitoring's new HQ at London's Broadcasting House. Crowsley Park House, an 18th-century mansion house, sits in its own grounds within the estate and is now a private residence. Smaller houses on the estate — South Lodge (at the main entrance to the park), North Lodge, Keeper's Cottage and Crowsley Park Lodge — are also privately occupied. The main house is Grade II listed on the National Heritage List for England. In addition to the house, the stable and coach house and the grotto in the grounds of the house are also Grade II listed. Woodland on the eastern and northern sides of the park, k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curtain Array
Curtain arrays are a class of large multielement directional radio transmitting wire antennas, used in the short-wave radio bands. They constitute a type of reflective array antenna, consisting of multiple wire dipole antennas, suspended in a vertical plane, often positioned in front of a "curtain" reflector made of a flat vertical screen of many long parallel wires. These are suspended by support wires strung between pairs of tall steel towers, reaching heights of up to high. Primarily employed for long-distance skywave (or ''skip'') transmission, they emit a beam of radio waves at a shallow angle into the sky just above the horizon, which is then reflected by the ionosphere back to Earth beyond the horizon. Curtain arrays are extensively used by international short-wave radio stations for broadcasting to large areas at transcontinental distances. Due to their powerful directional characteristics, curtain arrays are frequently utilized by government propaganda radio stations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Log Periodic Antenna
A log-periodic antenna (LP), also known as a log-periodic array or log-periodic aerial, is a multi-element, directional antenna designed to operate over a wide band of Frequency, frequencies. It was invented by John Dunlavy in 1952. The most common form of log-periodic antenna is the log-periodic dipole array or LPDA, The LPDA consists of a number of half-wave dipole driven elements of gradually increasing length, each consisting of a pair of metal rods. The dipoles are mounted close together in a line, connected in parallel to the feedline with alternating phase (waves), phase. Electrically, it simulates a series of two- or three-element Yagi–Uda antennas connected together, each set tuned to a different frequency. LPDA antennas look somewhat similar to Yagi antennas, in that they both consist of dipole rod elements mounted in a line along a support boom, but they work in very different ways. Adding elements to a Yagi increases its directionality, or Antenna gain, gain, whil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2023-10-28 14 34 48 "The Last Pole Standing" From The AT&T Pole Farm, On The Grounds Of The Reed-Bryan Farm At Mercer Meadows In Hopewell Township, Mercer County, New Jersey
In music theory, a trichord () is a group of three different pitch classes found within a larger group. A trichord is a contiguous three-note set from a musical scale or a twelve-tone row. In musical set theory there are twelve trichords given inversional equivalency, and, without inversional equivalency, nineteen trichords. These are numbered 1–12, with symmetrical trichords being unlettered and with uninverted and inverted nonsymmetrical trichords lettered A or B, respectively. They are often listed in prime form, but may exist in different voicings; different inversions at different transpositions. For example, the major chord, 3-11B (prime form: ,4,7, is an inversion of the minor chord, 3-11A (prime form: ,3,7. 3-5A and B are the Viennese trichord (prime forms: ,1,6and ,5,6. Historical Russian definition In late-19th to early 20th-century Russian musicology, the term trichord (трихорд ()) meant something more specific: a set of three pitches, each at least ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna (electronics)
In radio-frequency engineering, an antenna (American English) or aerial (British English) is an electronic device that converts an alternating current, alternating electric current into radio waves (transmitting), or radio waves into an electric current (receiving). It is the interface between radio waves Radio propagation, propagating through space and electric currents moving in metal Electrical conductor, conductors, used with a transmitter or receiver (radio), receiver. In transmission (telecommunications), transmission, a radio transmitter supplies an electric current to the antenna's Terminal (electronics), terminals, and the antenna radiates the energy from the current as electromagnetic radiation, electromagnetic waves (radio waves). In receiver (radio), reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be amplifier, amplified. Antennas are essential components ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Broadband
In telecommunications, broadband or high speed is the wide-bandwidth (signal processing), bandwidth data transmission that exploits signals at a wide spread of frequencies or several different simultaneous frequencies, and is used in fast Internet access. The transmission medium can be coaxial cable, optical fiber, wireless Internet (radio), twisted pair cable, or satellite broadband, satellite. Originally used to mean 'using a wide-spread frequency' and for services that were analog at the lowest level, nowadays in the context of Internet access, 'broadband' is often used to mean any high-speed Internet access that is seemingly always 'on' and is faster than Dial-up Internet access, dial-up access over traditional plain old telephone service, analog or ISDN public switched telephone network, PSTN services. The ideal telecommunication network has the following characteristics: ''broadband'', ''multi-media'', ''multi-point'', ''multi-rate'' and economical implementation for a di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shortwave
Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (approximately 100 to 10 metres in wavelength). It lies between the medium frequency band (MF) and the bottom of the VHF band. Radio waves in the shortwave band can be reflected or refracted from a layer of electrically charged atoms in the atmosphere called the ionosphere. Therefore, short waves directed at an angle into the sky can be reflected back to Earth at great distances, beyond the horizon. This is called skywave or "skip" propagation. Thus shortwave radio can be used for communication over very long distances, in contrast to radio waves of higher frequency, which travel in straight lines (line-of-sight propagation) and are generally limited by the visual horizon, about 64 km (40 miles). Shortwave broadcasts of radio pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Frequency
High frequency (HF) is the ITU designation for the band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred meters). Frequencies immediately below HF are denoted '' medium frequency'' (MF), while the next band of higher frequencies is known as the '' very high frequency'' (VHF) band. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called ''shortwave radio''. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as "skip" or "skywave" propagation – these frequencies can be used for long-distance communication across intercontinental distances and for mountainous terrains which prevent line-of-sight communications. The band is used by international shortwave broadcasting stations (3.95–25.8 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harald Friis
Harald Trap Friis (22 February 1893 – 15 June 1976), who published as H. T. Friis, was a Danish-American radio engineer whose work at Bell Laboratories included pioneering contributions to radio propagation, radio astronomy, and radar. His two Friis formulas remain widely used. Background Friis was born in Næstved, Denmark. In 1916, he received his electrical engineering degree from the Technical University of Denmark. After a stint at the Royal Gun Factory, in 1919 he received a Columbia University fellowship to study radio engineering under John H. Morecroft. In 1920 Friis joined a Western Electric Company research group which in 1925 became part of Bell Laboratories. There he remained for his entire professional career. Career Friis' first important publications were his 1923 Institute of Radio Engineers (IRE) paper on radio transmission measurements, 1925 IRE paper on directional antennas, and 1928 IRE paper on oscillographic observations of propagation ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edmond Bruce
Edmond Bruce (September 28, 1899 – November 28, 1973) was an American radio pioneer best known for creating the rhombic antenna and Bruce array. Bruce was born in Saint Louis, Missouri, and raised in Cambridge, Massachusetts, Brooklyn, and Washington, D.C. In 1917 he left high school to join the Navy and was eventually chief radio electrician in the transatlantic communication service, serving at the Otter Cliffs Radio Station in Bar Harbor, Maine. He then studied at George Washington University, 1919, and at Massachusetts Institute of Technology, 1920–1924, from which he received his bachelor's degree in electrical communication. From 1921 to 1923 he also worked for Melville Eastham's Clapp-Eastham Company. In 1924 he joined the Western Electric Company, and in 1925 became a research engineer at Bell Telephone Laboratories, where he helped develop short-wave radio receivers and field strength measuring equipment, and designed directional antennas for short-wave radio commu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
