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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] |
Biblis RFE RL 01
Biblis is a municipality in the Bergstraße district in southern Hesse, Germany. Geography Location The municipality lies in the Rhine rift west of the Odenwald between Darmstadt to the north and Mannheim to the south; it also lies north of Bürstadt. Biblis lies directly north of the lower reaches of the Weschnitz, which empties into the Rhine only a few kilometres northwest of the municipality. Neighbouring municipalities Biblis borders in the north on the municipalities of Groß-Rohrheim and Gernsheim, in the east on the municipality of Einhausen, in the south on the towns of Bürstadt and Lampertheim and in the west on the district-free city of Worms (Rhineland-Palatinate). Constituent communities Biblis's three ''Ortsteile'' are Biblis, Nordheim and Wattenheim. History In 836, Biblis had its first documentary mention in the Lorsch Abbey’s '' Codex Laureshamensis'' under the name ''Bibifloz'' (“settlement at the water”) when King Louis the German donated his ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell Telephone Company
The Bell Telephone Company was the initial corporate entity from which the Bell System originated to build a continental conglomerate and monopoly in telecommunication services in the United States and Canada. The company was organized in Boston, Massachusetts, on July 9, 1877, by Alexander Graham Bell's father-in-law Gardiner Greene Hubbard. A common law joint-stock company, the Bell Telephone Company was started on the basis of holding "potentially valuable patents", principally Bell's master telephone patent #174465. Upon inception, Hubbard was installed as trustee, although he was additionally the company's ''de facto'' president, since he also controlled his daughter's shares by power of attorney. Thomas Sanders, its principal financial backer, was treasurer. Hubbard also organized the New England Telephone and Telegraph Company, the first local operating company to offer service using Bell's telephone. Bell Telephone and New England Telephone merged on February 17, 1879, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Main Lobe
In a antenna (electronics), radio antennas, the main lobe or main beam is the region of the radiation pattern containing the highest Power (physics), power or exhibiting the greatest field strength. The radiation pattern of most antennas shows a pattern of "'':wikt:lobes, lobes''" at various directions, where the radiated signal strength reaches a local maximum, separated by "''null (radio), nulls''", at which the radiation falls to zero. In a directional antenna in which the objective is to emit the radio waves in one direction, the lobe in that direction is designed to have higher field strength than the others, so on a graph of the radiation pattern it appears biggest; this is the main lobe. The other lobes are called "''sidelobes''", and usually represent unwanted radiation in undesired directions. The sidelobe in the opposite direction from the main lobe is called the "''backlobe''". The radiation pattern referred to above is usually the horizontal radiation pattern, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horizontal Polarization
, or , is a property of transverse waves which specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. One example of a polarized transverse wave is vibrations traveling along a taut string, for example, in a musical instrument like a guitar string. Depending on how the string is plucked, the vibrations can be in a vertical direction, horizontal direction, or at any angle perpendicular to the string. In contrast, in longitudinal waves, such as sound waves in a liquid or gas, the displacement of the particles in the oscillation is always in the direction of propagation, so these waves do not exhibit polarization. Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves (shear waves) in solids. An electromagnetic wave such as light consists of a coupled oscillating electr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength
In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves), phase'' on the wave, such as two adjacent crests, troughs, or zero crossings. Wavelength is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The multiplicative inverse, inverse of the wavelength is called the ''spatial frequency''. Wavelength is commonly designated by the Greek letter lambda (''λ''). For a modulated wave, ''wavelength'' may refer to the carrier wavelength of the signal. The term ''wavelength'' may also apply to the repeating envelope (mathematics), envelope of modulated waves or waves formed by Interference (wave propagation), interference of several sinusoids. Assuming a sinusoidal wave moving at a fixed phase velocity, wave speed, wavelength is inversely proportion ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dipole Antenna
In radio and telecommunications a dipole antenna or doublet is one of the two simplest and most widely used antenna types, types of antenna; the other is the monopole antenna, monopole. The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole with a radiating structure supporting a line current so energized that the current has only one node at each far end. A dipole antenna commonly consists of two identical conductive elements such as metal wires or rods. The driving current from the transmitter is applied, or for receiving antennas the output signal to the radio receiver, receiver is taken, between the two halves of the antenna. Each side of the feedline to the transmitter or receiver is connected to one of the conductors. This contrasts with a monopole antenna, which consists of a single rod or conductor with one side of the feedline connected to it, and the other side connected to some type of g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Driven Element
In an antenna array made of multiple Electrical conductivity, conductive elements (typically metal rods), a driven element or active element (also called driven radiator or active radiator) is electrically connected to the radio receiver, receiver or transmitter while a parasitic element (or passive radiator) is not. Driven elements In a multielement antenna array (such as a Yagi–Uda antenna), the driven element or active element is the element in the antenna (typically a metal rod) which is electrically connected to the radio receiver, receiver or transmitter. In a transmitting antenna it is ''driven'' or ''excited'' by the radio frequency current from the transmitter, and is the source of the radio waves. In a receiving antenna it collects the incoming radio waves for reception, and converts them to tiny oscillating electric currents, which are applied to the radio receiver, receiver. Multielement antennas like the Yagi typically consist of a driven element, connected ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Liberty
Radio Free Europe/Radio Liberty (RFE/RL) is a media organization broadcasting news and analyses in 27 languages to 23 countries across Eastern Europe, Central Asia, the Caucasus, and the Middle East. Headquartered in Prague since 1995, RFE/RL operates 21 local bureaus with over 500 core staff, 1,300 freelancers, and 680 employees. Nicola Careem serves as the editor-in-chief. Founded during the Cold War, RFE began in 1949 targeting Soviet satellite states, while RL, established in 1951, focused on the Soviet Union. Initially funded covertly by the CIA until 1972, the two merged in 1976. RFE/RL was headquartered in Munich from 1949 to 1995, with additional broadcasts from Portugal's Glória do Ribatejo until 1996. Soviet authorities jammed their signals, and communist regimes often infiltrated their operations. Today, RFE/RL is a private 501(c)(3) corporation supervised by the United States Agency for Global Media, which oversees all government-supported international broa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voice Of America
Voice of America (VOA or VoA) is an international broadcasting network funded by the federal government of the United States that by law has editorial independence from the government. It is the largest and oldest of the American international broadcasters, producing digital, TV, and radio content in 48 languages for affiliate stations around the world.* * by * Its targeted and primary audience is non-Americans outside the American borders, especially those living in countries without press freedom or independent journalism. VOA was established in 1942, during World War II. Building on American use of shortwave radio during the war, it initially served as an anti-propaganda tool against Axis misinformation but expanded to include other forms of content like American music programs for cultural diplomacy. During the Cold War, its operations expanded in an effort to fight communism and played a role in the decline of communism in several countries. Throughout its operation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cold War
The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 until the dissolution of the Soviet Union in 1991. The term ''Cold war (term), cold war'' is used because there was no direct fighting between the two superpowers, though each supported opposing sides in regional conflicts known as proxy wars. In addition to the struggle for ideological and economic influence and an arms race in both conventional and Nuclear arms race, nuclear weapons, the Cold War was expressed through technological rivalries such as the Space Race, espionage, propaganda campaigns, Economic sanctions, embargoes, and sports diplomacy. After the end of World War II in 1945, during which the US and USSR had been allies, the USSR installed satellite state, satellite governments in its occupied territories in Eastern Europe and N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
