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Troposcatter
Tropospheric scatter, also known as troposcatter, is a method of communicating with microwave radio signals over considerable distances – often up to and further depending on frequency of operation, equipment type, terrain, and climate factors. This method of propagation uses the tropospheric scatter phenomenon, where radio waves at Ultra high frequency, UHF and Super high frequency, SHF Frequency, frequencies are randomly scattered as they pass through the upper layers of the troposphere. Radio signals are transmitted in a narrow beam aimed just above the horizon in the direction of the receiver station. As the signals pass through the troposphere, some of the energy is scattered back toward the Earth, allowing the receiver station to pick up the signal. Normally, signals in the microwave frequency range travel in straight lines, and so are limited to ''Line-of-sight propagation, line-of-sight'' applications, in which the receiver can be 'seen' by the transmitter. Communicat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropospheric Scatter
Tropospheric scatter, also known as troposcatter, is a method of communicating with microwave radio signals over considerable distances – often up to and further depending on frequency of operation, equipment type, terrain, and climate factors. This method of propagation uses the tropospheric scatter phenomenon, where radio waves at UHF and SHF frequencies are randomly scattered as they pass through the upper layers of the troposphere. Radio signals are transmitted in a narrow beam aimed just above the horizon in the direction of the receiver station. As the signals pass through the troposphere, some of the energy is scattered back toward the Earth, allowing the receiver station to pick up the signal. Normally, signals in the microwave frequency range travel in straight lines, and so are limited to '' line-of-sight'' applications, in which the receiver can be 'seen' by the transmitter. Communication distances are limited by the visual horizon to around . Troposcatter allow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microwave Relay
Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300MHz to 300GHz(1 m - 1 mm wavelength) of the electromagnetic spectrum. Microwave signals are normally limited to the line of sight, so long-distance transmission using these signals requires a series of repeaters forming a microwave relay network. It is possible to use microwave signals in over-the-horizon communications using tropospheric scatter, but such systems are expensive and generally used only in specialist roles. Although an experimental microwave telecommunication link across the English Channel was demonstrated in 1931, the development of radar in World War II provided the technology for practical exploitation of microwave communication. During the war, the British Army introduced the Wireless Set No. 10, which used microwave relays to multiplex eight telephone channels over long distances. A link across the English Channel allo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Alice Communications System
The White Alice Communications System (WACS, "White Alice" colloquially) was a United States Air Force telecommunication network with 80 radio stations constructed in Alaska during the Cold War. It used tropospheric scatter for over-the-horizon links and microwave relay for shorter line-of-sight links. Sites were characterized by large parabolic, tropospheric scatter antennas as well as smaller microwave dishes for point-to-point links. The system connected remote Air Force sites in Alaska, such as Aircraft Control and Warning (AC&W), Distant Early Warning Line (DEW Line) and Ballistic Missile Early Warning System (BMEWS), to command and control facilities and in some cases it was used for civilian phone calls. The network was originally operated by the USAF, but was turned over to RCA for operations after 1969. The opening of satellite communication links in the 1970s made the system obsolete, and in 1979 it was replaced by an RCA satellite link that connected all of the stations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ACE High
Allied Command Europe Highband, better known as ACE High, was a fixed service NATO radiocommunication and early warning system dating back to 1956. After extensive testing ACE High was accepted by NATO to become operational in 1964/1965. The frequency supportability and frequency assignments were profited in accordance with the NATO Joint Civil/Military Frequency Agreement (NJFA). The system was designed to be a combined UHF troposcatter/microwave radio system, providing long-range communications in the form of telephone, telegraph and data traffic in the NATO chain of command. Its combined services produced over 200 channels and equipment was in place to multiplex them to contain up to 12 different calls each. There used to be 49 troposcatter links augmented by 40 ''Line Of Sight'' Microwave terrestrial stations, located in nine different NATO countries from northern Norway through central Europe to eastern Turkey. The transmitters broadcast at 832.56 - 959.28 MHz pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microwave Radio
Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300MHz to 300GHz(1 m - 1 mm wavelength) of the electromagnetic spectrum. Microwave signals are normally limited to the line of sight, so long-distance transmission using these signals requires a series of repeaters forming a microwave relay network. It is possible to use microwave signals in over-the-horizon communications using tropospheric scatter, but such systems are expensive and generally used only in specialist roles. Although an experimental microwave telecommunication link across the English Channel was demonstrated in 1931, the development of radar in World War II provided the technology for practical exploitation of microwave communication. During the war, the British Army introduced the Wireless Set No. 10, which used microwave relays to multiplex eight telephone channels over long distances. A link across the English Channel allowe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pole Vault (communications System)
Pole Vault was the first operational tropospheric scatter communications system. It linked radar sites and military airfields in Greenland and eastern Canada by telephone to send aircraft tracking and warning information across North America. The line stretched from Thule Air Force Base in northern Greenland, to Baffin Island and then along the eastern coast of Labrador and Newfoundland to St. John's for connection into existing commercial telecommunications networks. The system was first proposed in 1952 to send information along the isolated Pinetree Line stations on the Labrador coast. This led to an initial proposal to use a microwave relay system, a relatively new technology at the time. The network would require 50 relays, many of them in the wilderness. Bell Canada won the contract to build the system after the USAF was convinced they could handle the job. Before construction began, Bell learned of experiments with long-range troposcatter systems being carried out i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultra High Frequency
Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (one decimeter). Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF (very high frequency) or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, satellite phones, and numerous other applications. The IEEE defines the UHF radar band as frequencies between 300 MHz and 1 GHz. Two other IEEE radar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lincoln Labs
The MIT Lincoln Laboratory, located in Lexington, Massachusetts, is a United States Department of Defense federally funded research and development center chartered to apply advanced technology to problems of national security. Research and development activities focus on long-term technology development as well as rapid system prototyping and demonstration. Its core competencies are in sensors, integrated sensing, signal processing for information extraction, decision-making support, and communications. These efforts are aligned within ten mission areas. The laboratory also maintains several field sites around the world. The laboratory transfers much of its advanced technology to government agencies, industry, and academia, and has launched more than 100 start-ups. History Origins At the urging of the United States Air Force, the Lincoln Laboratory was created in 1951 at the Massachusetts Institute of Technology (MIT) as part of an effort to improve the U.S. air defense syst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NATO
The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two North American. Established in the aftermath of World War II, the organization implemented the North Atlantic Treaty, signed in Washington, D.C., on 4 April 1949. NATO is a collective security system: its independent member states agree to defend each other against attacks by third parties. During the Cold War, NATO operated as a check on the perceived threat posed by the Soviet Union. The alliance remained in place after the dissolution of the Soviet Union and has been involved in military operations in the Balkans, the Middle East, South Asia, and Africa. The organization's motto is '' animus in consulendo liber'' (Latin for "a mind unfettered in deliberation"). NATO's main headquarters are located in Brussels, Belgium, while ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe and Asia from the "New World The term ''New World'' is often used to mean the majority of Earth's Western Hemisphere, specifically the Americas."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: Oxford University Press, p. ..." of the Americas in the European perception of Earth, the World. The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Europe and Africa to the east, and North America, North and South America to the west. As one component of the interconnected World Ocean, it is connected in the north to the Arctic Ocean, to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south (other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DEW Line
The Distant Early Warning Line, also known as the DEW Line or Early Warning Line, was a system of radar stations in the northern Arctic region of Canada, with additional stations along the north coast and Aleutian Islands of Alaska (see Project Stretchout and Project Bluegrass), in addition to the Faroe Islands, Greenland, and Iceland. It was set up to detect incoming bombers of the Soviet Union during the Cold War, and provide early warning of any sea-and-land invasion. The DEW Line was the northernmost and most capable of three radar lines in Canada and Alaska. The first of these was the joint Canadian-United States Pinetree Line, which ran from Newfoundland to Vancouver Island just north of the Canada–United States border, but even while it was being built there were concerns that it would not provide enough warning time to launch an effective counterattack. The Mid-Canada Line (MCL) was proposed as an inexpensive solution using bistatic radar. This provided a "trip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mid-Canada Line
The Mid-Canada Line (MCL), also known as the McGill Fence, was a line of radar stations running east–west across the middle of Canada, used to provide early warning of a Soviet bomber attack on North America. It was built to supplement the Pinetree Line, which was located farther south. The majority of Mid-Canada Line stations were used only briefly from the late 1950s to the mid-1960s, as the attack threat changed from bombers to ICBMs. As the MCL was closed down, the early warning role passed almost entirely to the newer and more capable DEW Line farther north. The MCL was based on the bistatic radar principle, using separated transmitters and receivers. An aircraft flying anywhere between the stations would reflect some of the transmitted signal towards the receiver, where it would mix with the signal travelling directly from the transmitter. The mixing of the two signals produces a pattern that is very easy to detect using simple electronics. As the transmitter is not pu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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