Tropospheric scatter, also known as troposcatter, is a method of communicating with

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 limi ...

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 Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

are randomly scattered as they pass through the upper layers of the

troposphere The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. From ...

. 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 allows microwave communication beyond the horizon. It was developed in the 1950s and used for military communications until

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...

s largely replaced it in the 1970s. Because the troposphere is turbulent and has a high proportion of moisture, the tropospheric scatter radio signals are

refracted In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...

and consequently only a tiny proportion of the transmitted radio energy is collected by the receiving antennas. Frequencies of transmission around are best suited for tropospheric scatter systems as at this frequency the wavelength of the signal interacts well with the moist, turbulent areas of the troposphere, improving

signal-to-noise ratio Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in deci ...

Overview

Discovery

Previous to

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, prevailing radio physics theory predicted a relationship between frequency and diffraction that suggested radio signals would follow the curvature of the Earth, but that the strength of the effect would fall off rapidly and especially at higher frequencies. However, during the war, there were numerous incidents in which high-frequency radar signals were able to detect targets at ranges far beyond the theoretical calculations. In spite of these repeated instances of anomalous range, the matter was never seriously studied. In the immediate post-war era, the limitation on

television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...

construction was lifted in the United States and millions of sets were sold. This drove an equally rapid expansion of new television stations. Based on the same calculations used during the war, the

Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdiction ...

(FCC) arranged frequency allocations for the new VHF and UHF channels to avoid interference between stations. To everyone's surprise, interference was common, even between widely separated stations. As a result, licenses for new stations were put on hold in what is known as the "television freeze" of 1948.

Bell Labs Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mult ...

was among the many organizations that began studying this effect, and concluded it was a previously unknown type of reflection off the

tropopause The tropopause is the atmospheric boundary that demarcates the troposphere from the stratosphere; which are two of the five layers of the atmosphere of Earth. The tropopause is a thermodynamic gradient-stratification layer, that marks the end of ...

. This was limited to higher frequencies, in the UHF and microwave bands, which is why it had not been seen prior to the war when these frequencies were beyond the ability of existing electronics. Although the vast majority of the signal went through the troposphere and on to space, the tiny amount that was reflected was useful if combined with powerful transmitters and very sensitive receivers. In 1952, Bell began experiments with

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 de ...

, the MIT-affiliated

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

research lab. Using Lincoln's powerful microwave transmitters and Bell's sensitive receivers, they built several experimental systems to test a variety of frequencies and weather effects. When

Bell Canada Bell Canada (commonly referred to as Bell) is a Canadian telecommunications company headquartered at 1 Carrefour Alexander-Graham-Bell in the borough of Verdun in Montreal, Quebec, Canada. It is an ILEC (incumbent local exchange carrier) in t ...

heard of the system they felt it might be useful for a new communications network in

Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 ...

and took one of the systems there for cold weather testing. In 1954 the results from both test series were complete and construction began on the first troposcatter system, the

Pole Vault Pole vaulting, also known as pole jumping, is a track and field event in which an athlete uses a long and flexible pole, usually made from fiberglass or carbon fiber, as an aid to jump over a bar. Pole jumping competitions were known to the Myc ...

system that linked

Pinetree Line The Pinetree Line was a series of radar stations located across the northern United States and southern Canada at about the 50th parallel north, along with a number of other stations located on the Atlantic Ocean, Atlantic and Pacific coasts. ...

radar systems along the coast of

Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 ...

. Using troposcatter reduced the number of stations from 50

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 limi ...

s scatted through the wilderness to only 10, all located at the radar stations. In spite of their higher unit costs, the new network cost half as much to build as a relay system. Pole Vault was quickly followed by similar systems like

White Alice 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 l ...

, relays on the

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 ...

and the

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 Proj ...

, and during the 1960s, across the

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 Europe as part of

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 No ...

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 fr ...

system.

Use

The

propagation loss In underwater acoustics, propagation loss is a measure of the reduction in sound intensity as the sound propagates away from an underwater sound source. It is defined as the difference between the source level and the received sound pressure level ...

es are very high; only about one trillionth () of the transmit power is available at the receiver. This demands the use of antennas with extremely large antenna gain. The original Pole Vault system used large

parabolic reflector A parabolic (or paraboloid or paraboloidal) reflector (or dish or mirror) is a reflective surface used to collect or project energy such as light, sound, or radio waves. Its shape is part of a circular paraboloid, that is, the surface generated ...

dish antennas, but these were soon replaced by billboard antennas which were somewhat more robust, an important quality given that these systems were often found in harsh locales. Paths were established at distances over . They required antennas ranging from and amplifiers ranging from to . These were analogue systems which were capable of transmitting a few voice channels. Troposcatter systems have evolved over the years. With

communication satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...

s used for long-distance communication links, current troposcatter systems are employed over shorter distances than previous systems, use smaller antennas and amplifiers, and have much higher bandwidth capabilities. Typical distances are between , though greater distances can be achieved depending on the climate, terrain, and data rate required. Typical antenna sizes range from while typical amplifier sizes range from to . Data rates over can be achieved with today's technology. Tropospheric scatter is a fairly secure method of propagation as dish alignment is critical, making it extremely difficult to intercept the signals, especially if transmitted across open water, making them highly attractive to military users. Military systems have tended to be ‘thin-line’ tropo – so called because only a narrow

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

‘information’ channel was carried on the tropo system; generally up to 32 analogue ( bandwidth) channels. Modern military systems are "wideband" as they operate 4-16 Mbit/s digital data channels. Civilian troposcatter systems, such as the

British Telecom BT Group plc (trade name, trading as BT and formerly British Telecom) is a British Multinational corporation, multinational telecommunications holding company headquartered in London, England. It has operations in around 180 countries and is th ...

(BT)

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

oil communications network, required higher capacity ‘information’ channels than were available using HF (high frequency – to ) radio signals, before satellite technology was available. The BT systems, based at

Scousburgh Scousburgh is a small community in the parish of Dunrossness, in the South Mainland Mainland is defined as "relating to or forming the main part of a country or continent, not including the islands around it egardless of status under territo ...

in the

Shetland Islands Shetland, also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in Scotland lying between Orkney, the Faroe Islands and Norway. It is the northernmost region of the United Kingdom. The islands lie about to the no ...

Mormond Hill Mormond Hill (Scottish Gaelic A' Mhormhonadh, meaning the great hill or moor; known as ''Mormounth'' in Old Scots) is a large hill in Aberdeenshire, Scotland, not far from Fraserburgh. Its peak is .Aberdeenshire Aberdeenshire ( sco, Aiberdeenshire; gd, Siorrachd Obar Dheathain) is one of the 32 Subdivisions of Scotland#council areas of Scotland, council areas of Scotland. It takes its name from the County of Aberdeen which has substantially differe ...

and Row Brow near

Scarborough Scarborough or Scarboro may refer to: People * Scarborough (surname) * Earl of Scarbrough Places Australia * Scarborough, Western Australia, suburb of Perth * Scarborough, New South Wales, suburb of Wollongong * Scarborough, Queensland, su ...

, were capable of transmitting and receiving 156 analogue ( bandwidth) channels of data and telephony to / from North Sea oil production platforms, using

frequency-division multiplexing In telecommunications, frequency-division multiplexing (FDM) is a technique by which the total bandwidth available in a communication medium is divided into a series of non-overlapping frequency bands, each of which is used to carry a separate ...

(FDMX) to combine the channels. Because of the nature of the turbulence in the troposphere, quadruple diversity propagation paths were used to ensure reliability of the service, equating to about 3 minutes of downtime due to propagation drop out per month. The quadruple space and polarisation diversity systems needed two separate dish antennas (spaced several metres apart) and two differently polarised

feed horn A feed horn (or feedhorn) is a small horn antenna used to couple a waveguide to e.g. a parabolic dish antenna or offset dish antenna for reception or transmission of microwave. A typical application is the use for satellite television recep ...

s – one using vertical polarisation, the other using horizontal polarisation. This ensured that at least one signal path was open at any one time. The signals from the four different paths were recombined in the receiver where a phase corrector removed the

phase difference In physics and mathematics, the phase of a periodic function F of some real variable t (such as time) is an angle-like quantity representing the fraction of the cycle covered up to t. It is denoted \phi(t) and expressed in such a scale that it v ...

s of each signal. Phase differences were caused by the different path lengths of each signal from transmitter to receiver. Once phase corrected, the four signals could be combined additively. Atmosphere layers-en

Tropospheric scatter communications networks

The tropospheric scatter phenomenon has been used to build both civilian and military communication links in a number of parts of the world, including: ; Allied Command Europe Highband (ACE High), :

military

radiocommunication Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...

and

early warning An early warning system is a warning system that can be implemented as a Poset, chain of information communication systems and comprises sensors, Detection theory, event detection and decision support system, decision subsystems for early identi ...

system throughout Europe from the Norwegian-Soviet border to the Turkish-Soviet border. ; BT (British Telecom), :

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

Shetland Shetland, also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in Scotland lying between Orkney, the Faroe Islands and Norway. It is the northernmost region of the United Kingdom. The islands lie about to the no ...

Mormond Hill Mormond Hill (Scottish Gaelic A' Mhormhonadh, meaning the great hill or moor; known as ''Mormounth'' in Old Scots) is a large hill in Aberdeenshire, Scotland, not far from Fraserburgh. Its peak is .Fernmeldeturm Berlin The Fernmeldeturm Berlin (Telecommunications Tower Berlin) is a telecommunication tower located atop the Schäferberg hill in Berlin-Wannsee. The tower was built between 1961 and 1964, and is not open to the public. Owner and operator of the site ...

, :Torfhaus-Berlin, Clenze-Berlin at Cold War times ;

Portugal Telecom Altice Portugal (formerly known as Portugal Telecom or PT) is the largest telecommunications service provider in Portugal. Since June 2, 2015, the company has been a wholly owned subsidiary of Altice Europe, a multinational cable and telecommuni ...

, :Serra de Nogueira (northeastern Portugal) to Artzamendi (southwestern France) ;

CNCP Telecommunications CNCP Telecommunications (Canadian National-Canadian Pacific Telecommunications) was an electrical telegraph operator and later a telecom company, which operated between 1967 and 1990. CNCP was created as a joint venture between the Canadian Nat ...

, :

Tsiigehtchic Tsiigehtchic ( ; "mouth of the iron river"), officially the ''Charter Community of Tsiigehtchic'', is a Gwich'in community located at the confluence of the Mackenzie and the Arctic Red Rivers, in the Inuvik Region of the Northwest Territories, ...

to Galena Hill, Keno City : Hay River -

Port Radium Port Radium is a mining area on the eastern shore of Great Bear Lake, Northwest Territories, Canada. It included the settlement of Cameron Bay as well as the Eldorado (also called Port Radium) and Echo Bay mines. The name Port Radium did n ...

- Lady Franklin Point ; - :

Guanabo town in province is a beach town in the Ciudad de la Habana Province of Cuba. It is a ward (''consejo popular'') located within the municipality of Habana del Este halfway between the centre of Havana and Santa Cruz del Norte, at the mouth of the ...

Florida City Florida City is a city in Miami-Dade County, Florida, United States. It is the southernmost municipality in the South Florida metropolitan area. Florida City is primarily a Miami suburb and a major agricultural area. As of the 2020 census, it ...

;Project Offices -

AT&T Corporation AT&T Corporation, originally the American Telephone and Telegraph Company, is the subsidiary of AT&T Inc. that provides voice, video, data, and Internet telecommunications and professional services to businesses, consumers, and government agen ...

, : :Project Offices is the name sometimes used to refer to several structurally dependable facilities maintained by the ATT Corporation in the Mid-Atlantic states since the mid-th century to house an ongoing, non-public, company project. AT&T began constructing Project Offices in the . Since the inception of the Project Offices program, the company has chosen not to disclose the exact nature of business conducted at Project Offices. However, it has described them as ''central facilities''. ::* Pittsboro,

North Carolina North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...

::*

Buckingham Buckingham ( ) is a market town in north Buckinghamshire, England, close to the borders of Northamptonshire and Oxfordshire, which had a population of 12,890 at the 2011 Census. The town lies approximately west of Central Milton Keynes, sou ...

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

::*

Charlottesville Charlottesville, colloquially known as C'ville, is an independent city in the Commonwealth of Virginia. It is the county seat of Albemarle County, which surrounds the city, though the two are separate legal entities. It is named after Queen Ch ...

::* Leesburg,

::* Hagerstown,

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

;Texas Towers - Air defence radars, :The Texas Towers were a set of three

facilities off the eastern seaboard of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

which were used for surveillance by the

United States Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...

during the

Cold War The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...

. Modeled on the offshore oil drilling platforms first employed off the

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

coast, they were in operation from 1958 to 1963. : ;

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 P ...

, :A series of five stations (070, 060, 050, 415, 410) in

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

and

Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...

around the lower

Hudson Bay Hudson Bay ( crj, text=ᐐᓂᐯᒄ, translit=Wînipekw; crl, text=ᐐᓂᐹᒄ, translit=Wînipâkw; iu, text=ᑲᖏᖅᓱᐊᓗᒃ ᐃᓗᐊ, translit=Kangiqsualuk ilua or iu, text=ᑕᓯᐅᔭᕐᔪᐊᖅ, translit=Tasiujarjuaq; french: b ...

. A series of six stations were built in Labrador and Quebec between Goose Bay and Sept-Îles between 1957–1958. ;

, :

was series of fourteen stations providing communications for Eastern seaboard radar stations of the US/Canadian Pinetree line, running from N-31

Frobisher Bay Frobisher Bay is an inlet of the Davis Strait in the Qikiqtaaluk Region of Nunavut, Canada. It is located in the southeastern corner of Baffin Island. Its length is about and its width varies from about at its outlet into the Labrador Sea ...

Baffin Island Baffin Island (formerly Baffin Land), in the Canadian territory of Nunavut, is the largest island in Canada and the fifth-largest island in the world. Its area is , slightly larger than Spain; its population was 13,039 as of the 2021 Canadia ...

to N-22

St. John's, Newfoundland St. John's is the capital and largest city of the Canadian province of Newfoundland and Labrador, located on the eastern tip of the Avalon Peninsula on the island of Newfoundland. The city spans and is the easternmost city in North America ...

. ;

DEW Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening due to condensation. As the exposed surface cools by radiating its heat, atmospheric moisture condenses at a rate greater than that at wh ...

Training (

era), / :A former military and civil communications network with eighty stations stretching up the western seaboard from

Port Hardy Port Hardy is a district municipality in British Columbia, Canada located on the north-east end of Vancouver Island. Port Hardy has a population of 4,132 as of the last census (2016). It is the gateway to Cape Scott Provincial Park, the North Co ...

Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian Provinces and territories of Canada, province of British Columbia. The island is in length, in width at its widest point, and in total area, while are o ...

north to Barter Island (BAR), west to

Shemya, Alaska Shemya or Simiya ( ale, Samiyax̂) is a small island in the Semichi Islands group of the Near Islands chain in the Aleutian Islands archipelago southwest of Alaska, at . It has a land area of , and is about southwest of Anchorage, Alaska. It is ...

(SYA) in the

Aleutian Islands The Aleutian Islands (; ; ale, Unangam Tanangin,”Land of the Aleuts", possibly from Chukchi language, Chukchi ''aliat'', "island"), also called the Aleut Islands or Aleutic Islands and known before 1867 as the Catherine Archipelago, are a cha ...

(just a few hundred miles from the

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...

) and east across arctic

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

. Note that not all station were troposcatter, but many were. It also included a training facility for White Alice/DEW line tropo-scatter network located between

Pecatonica, Illinois Pecatonica is a village in Winnebago County, Illinois, United States. It is part of the Rockford, Illinois Metropolitan Statistical Area. The population was 2,195 at the 2010 census, up from 1,997 in 2000. History The village was named afte ...

Streator, Illinois Streator is a city in LaSalle and Livingston counties in the U.S. state of Illinois. The city is situated on the Vermilion River approximately southwest of Chicago in the prairie and farm land of north-central Illinois. As of the 2020 censu ...

. ;

(Post

era), / :Several tropo-scatter networks providing communications for the extensive air-defence radar chain in the far north of Canada and the US. ; North Atlantic Radio System (NARS), :NATO air-defence network stretching from

RAF Fylingdales Royal Air Force Fylingdales or more simply RAF Fylingdales is a Royal Air Force station on Snod Hill in the North York Moors, England. Its motto is "Vigilamus" (translates to "We are watching"). It is a radar base and is also part of the Ball ...

, via Mormond Hill, UK, Sornfelli (

Faroe Islands The Faroe Islands ( ), or simply the Faroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic island group and an autonomous territory of the Kingdom of Denmark. They are located north-northwest of Scotland, and about halfway bet ...

), Höfn, Iceland to Keflavik DYE-5, Rockville. ;European Tropospheric Scatter - Army (ET-A), :A US Army network from

to a network in Germany and a single station in France (Maison Fort). The network became active on 1966. ;486L Mediterranean Communications System (MEDCOM), : A network covering the European coast of the Mediterranean Sea from San Pablo airport, San Pablo, Spain in the west to Incirlik Air Base, Turkey in the East, with headquarters at RAF Ringstead, Ringstead in Dorset, England. Commissioned by the US Air Force in . ;Royal Air Force, :Communications to British Forces Germany, running from Swingate in Kent to Lammersdorf in Germany. ;:de:Troposphären-Nachrichtensystem Bars, Troposphären-Nachrichtensystem Bars, Warsaw Pact Bars_a

:A Warsaw Pact tropo-scatter network stretching from near Rostok in the East Germany, DDR (Deutsches Demokratisches Republik), Czechoslovakia, Hungary, Poland, Byelorussian Soviet Socialist Republic, Byelorussia USSR, Ukrainian Soviet Socialist Republic, Ukraine USSR and Bulgaria. ;TRRL SEVER, :A Soviet network stretching across the USSR. ; - Troposcatter link stamp of India-1982

:A single section from Srinigar, Kashmir, India to Dangara, Tajikistan, USSR. ;Indian Air Force, :Part of an Air Defence Network covering major air bases, radar installations and missile sites in Northern and central India. The network is being phased out to be replaced with more modern fiber-optic based communication systems. ;Peace Ruby, Spellout, Peace Net, :An air-defence network set up by the

prior to the Iranian Revolution, 1979 Islamic Revolution. ''Spellout'' built a radar and communications network in the north of Iran. ''PeaceRuby'' built another air-defence network in the south and ''PeaceNet'' integrated the two networks. ; - :A tropo-scatter system linking Al Manamah, Bahrain to Dubai, United Arab Emirates. ;Royal Air Force of Oman, :A tropo-scatter communications system providing military comms to the former SOAF - Sultan of Oman's Air Force, (now RAFO - Royal Air Force of Oman), across the Sultanate of Oman. ;Royal Saudi Air Force, :A Royal Saudi Air Force tropo-scatter network linking major airbases and population centres in Saudi Arabia. ;Yemen, :A single system linking Sana'a with Sa'dah. ;BACK PORCH and Integrated Wideband Communications System (IWCS), :Two networks run by the

linking military bases in Thailand and South Vietnam. Stations were located at Bangkok, Ubon Royal Thai Air Force Base, Pleiku, Nha Trang, Vung Chua mountain () Quy Nhon, Monkey Mountain Facility Da Nang, Phu Bai Combat Base, Pr Line () near Da Lat, Hon Cong mountain An Khê, Phu Lam () Saigon, VC Hill () Vũng Tàu and Cần Thơ. ;Phil-Tai-Oki, :A system linking the Taiwan with the Philippines and Okinawa. ; Cable & Wireless plc, Cable & Wireless Caribbean network :A troposcatter link was established by Cable & Wireless in 1960, linking Barbados with Port of Spain, Trinidad. The network was extended further south to Georgetown, Guyana in 1965. ;Japanese Troposcatter Networks, :Two networks linking Japanese islands from North to South.

Tactical Troposcatter Communication systems

As well as the permanent networks detailed above, there have been many tactical transportable systems produced by several countries: ;Soviet / Russian Troposcatter Systems :MNIRTI R-423-1 Brig-1/R-423-2A Brig-2A/R-423-1KF :MNIRTI R-444 Eshelon / R-444-7,5 Eshelon D :MNIRTI R-420 Atlet-D :NIRTI R-417 Baget/R-417S Baget S :NPP Radiosvyaz R-412 A/B/F/S TORF :MNIRTI R-410/R-410-5,5/R-410-7,5 Atlet / Albatros :MNIRTI R-408/R-408M Baklan ;People's Republic of China (PRoC), People's Liberation Army (PLA) Troposcatter Systems :CETC TS-504 Troposcatter Communication System :CETC TS-510/GS-510 Troposcatter Communication System ;Western Troposcatter Systems :AN/TRC-97 Troposcatter Communication System :AN/TRC-170 Tropospheric Scatter Microwave Radio Terminal :AN/GRC-201 Troposcatter Communication System Tropo Scatter Microwave System Antenna

The U.S. Army and Air Force use tactical tropospheric scatter systems developed by Raytheon for long haul communications. The systems come in two configurations, the original "heavy tropo", and a newer "light tropo" configuration exist. The systems provide four Multiplexing, multiplexed group channels and trunk encryption, and 16 or 32 local analog phone extensions. The U.S. Marine Corps also uses the same device, albeit an older version.

References

Citations

Bibliography

External links

Russian tropospheric relay communication network

Tropospheric Scatter Communications - the essentials
* {{Authority control Radio frequency propagation Atmospheric optical phenomena