Tropospheric scatter

Last updated
A tropospheric scatter system can bridge large distances while a microwave relay system (below) requires multiple relay stations due to its line of sight limitation. Tropospheric scatter.jpg
A tropospheric scatter system can bridge large distances while a microwave relay system (below) requires multiple relay stations due to its line of sight limitation.
Boswell Bay, Alaska White Alice Site, Tropospheric scatter antenna and feeder. White Alice Site, Tropospheric Antennas HAER AK-21-A-2.jpg
Boswell Bay, Alaska White Alice Site, Tropospheric scatter antenna and feeder.
Pacific Scatter System Pacific Scatter.jpg
Pacific Scatter System

Tropospheric scatter, also known as troposcatter, is a method of communicating with microwave radio signals over considerable distances – often up to 500 kilometres (310 mi) 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. [1]

Contents

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 48–64 kilometres (30–40 mi). Troposcatter allows microwave communication beyond the horizon. It was developed in the 1950s and used for military communications until communications satellites 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 and consequently only a tiny proportion of the transmitted radio energy is collected by the receiving antennas. Frequencies of transmission around 2GHz 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 ratios.

Overview

Discovery

Previous to World War II, 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. [2]

In the immediate post-war era, the limitation on television 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 (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. [2]

Bell Labs was among the many organizations that began studying this effect, and concluded it was a previously unknown type of reflection off the tropopause. 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-affiliated radar 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 heard of the system they felt it might be useful for a new communications network in Labrador and took one of the systems there for cold weather testing. [2]

In 1954 the results from both test series were complete and construction began on the first troposcatter system, the Pole Vault system that linked Pinetree Line radar systems along the coast of Labrador. Using troposcatter reduced the number of stations from 50 microwave relays 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, relays on the Mid-Canada Line and the DEW Line, and during the 1960s, across the Atlantic Ocean and Europe as part of NATO's ACE High system.

Use

Pole Vault used circular parabolic antennas, later systems generally used squared-off versions sometimes known as "billboards". Tropo Scatter communications.jpg
Pole Vault used circular parabolic antennas, later systems generally used squared-off versions sometimes known as "billboards".

The propagation losses are very high; only about one trillionth (10×10^−12) 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 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 1,000 kilometres (620 mi). They required antennas ranging from 9 to 36 metres (30 to 118 ft) and amplifiers ranging from 1 kW to 50 kW. These were analogue systems which were capable of transmitting a few voice channels.

Troposcatter systems have evolved over the years. With communication satellites 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 50 to 250 kilometres (31 to 155 mi), though greater distances can be achieved depending on the climate, terrain, and data rate required. Typical antenna sizes range from 1.2 to 12 metres (3 ft 11 in to 39 ft 4 in) while typical amplifier sizes range from 10 W to 2 kW. Data rates over 20 Mbit/s 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 ‘information’ channel was carried on the tropo system; generally up to 32 analogue (4kHz 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) North Sea oil communications network, required higher capacity ‘information’ channels than were available using HF (high frequency – 3MHz to 30MHz) radio signals, before satellite technology was available. The BT systems, based at Scousburgh in the Shetland Islands, Mormond Hill in Aberdeenshire and Row Brow near Scarborough, were capable of transmitting and receiving 156 analogue (4kHz bandwidth) channels of data and telephony to / from North Sea oil production platforms, using frequency-division multiplexing (FDMX) to combine the channels.

Because of the nature of the turbulence in the troposphere, quadruple diversity propagation paths were used to ensure

Atmosphere layers-en.svg

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), Flag of NATO.svg  NATO
NATO military radiocommunication and early warning system throughout Europe from the Norwegian-Soviet border to the Turkish-Soviet border.
BT (British Telecom), Flag of the United Kingdom.svg  UK
United Kingdom - Shetland to Mormond Hill
Fernmeldeturm Berlin, Flag of Germany.svg  West Germany
Torfhaus-Berlin, Clenze-Berlin at Cold War times
Portugal Telecom, Flag of Portugal.svg  Portugal
Serra de Nogueira (northeastern Portugal) to Artzamendi (southwestern France)
CNCP Telecommunications, Flag of Canada (Pantone).svg  Canada
Tsiigehtchic to Galena Hill, Keno City
Hay River - Port Radium - Lady Franklin Point
Flag of Cuba.svg  Cuba - Flag of Florida.svg  Florida
Guanabo to Florida City
Project Offices - AT&T Corporation, Flag of the United States.svg  United States
Project Offices is the name sometimes used to refer to several structurally dependable facilities maintained by the AT&T Corporation in the Mid-Atlantic states since the mid-20th century to house an ongoing, non-public, company project. AT&T began constructing Project Offices in the 1960s. 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. [3] [4] [5]
Texas Towers - Air defence radars, Flag of the United States Air Force.svg  United States Air Force
The Texas Towers were a set of three radar facilities off the eastern seaboard of the United States which were used for surveillance by the United States Air Force during the Cold War. Modeled on the offshore oil drilling platforms first employed off the Texas coast, they were in operation from 1958 to 1963.
Tower IDLocationStaffing unitMainland stationNotes
TT-1Cashes Ledge off New Hampshire coast
42°53′N68°57′W / 42.883°N 68.950°W / 42.883; -68.950
Not built
TT-2 Georges Bank off Cape Cod
41°45′0.00″N67°46′0.00″W / 41.7500000°N 67.7666667°W / 41.7500000; -67.7666667
762d Radar Squadron North Truro Air Force Station decommissioned 1963
TT-3 Nantucket Shoals
40°45′00.00″N69°19′0.00″W / 40.7500000°N 69.3166667°W / 40.7500000; -69.3166667
773d Radar Squadron Montauk AFS decommissioned 1963
TT-4 off Long Beach Island, New Jersey
39°48′N72°40′W / 39.800°N 72.667°W / 39.800; -72.667
646th Radar Squadron Highlands Air Force Station collapsed (1961)
TT-5 Browns Bank south of Nova Scotia
42°47′N65°37′W / 42.783°N 65.617°W / 42.783; -65.617
Not built
Mid Canada Line, Flag of Canada (Pantone).svg  Canada
A series of five stations (070, 060, 050, 415, 410) in Ontario and Quebec around the lower Hudson Bay.
Pinetree Line, Pole Vault, Flag of Canada (Pantone).svg  Canada
A series of fourteen stations providing communications for Eastern seaboard radar stations of the US/Canadian Pinetree line, running from N-31 Frobisher Bay, Baffin Island to St. John's, Newfoundland and Labrador.
White Alice/DEW Line/DEW Training (Cold War era), Flag of the United States.svg  United States/Flag of Canada (Pantone).svg  Canada
A former military and civil communications network with eighty stations stretching up the western seaboard from Port Hardy, Vancouver Island north to Barter Island (BAR), west to Shemya, Alaska (SYA) in the Aleutian Islands (just a few hundred miles from the Soviet Union) and east across arctic Canada to Greenland. 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 to Streator, Illinois.
DEW Line (Post Cold War era), Flag of the United States.svg  United States/Flag of Canada (Pantone).svg  Canada
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), Flag of NATO.svg  NATO
NATO air-defence network stretching from RAF Fylingdales, via Mormond Hill, UK, Sornfelli (Faroe Islands), Höfn, Iceland to Keflavik DYE-5, Rockville.
European Tropospheric Scatter - Army (ET-A), Flag of the United States Army.svg  United States Army
A US Army network from RAF Fylingdales to a network in Germany and a single station in France (Maison Fort). The network became active on 1966. [8]
486L Mediterranean Communications System (MEDCOM), Flag of the United States Air Force.svg  United States Air Force
A network covering the European coast of the Mediterranean Sea from San Pablo, Spain in the west to Incirlik Air Base, Turkey in the East, with headquarters at Ringstead in Dorset, England. Commissioned by the US Air Force in 1966. [9] :Spanish Communications Region
Royal Air Force, Flag of the United Kingdom.svg  UK
Communications to British Forces Germany, running from Swingate in Kent to Lammersdorf in Germany.
Troposphären-Nachrichtensystem Bars, Warsaw Pact
BARS tropo-scatter network map Bars a.jpg
BARS tropo-scatter network map
A Warsaw Pact tropo-scatter network stretching from near Rostok in the DDR (Deutsches Demokratisches Republik), Czechoslovakia, Hungary, Poland, Byelorussia USSR, Ukraine USSR, Romania and Bulgaria.
TRRL SEVER, Flag of the Soviet Union.svg  Soviet Union
A Soviet network stretching across the USSR. [10]
Flag of India.svg  India - Flag of the Soviet Union.svg  Soviet Union
India-USSR troposcatter UHF link on a 1982 stamp of India Troposcatter link stamp of India-1982.jpg
India-USSR troposcatter UHF link on a 1982 stamp of India
A single section from Srinigar, Kashmir, India to Dangara, Tajikistan, USSR.
Indian Air Force, Flag of India.svg  India
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. [11]
Peace Ruby, Spellout, Peace Net, Flag of Iran.svg  Imperial State of Iran
An air-defence network set up by the United States prior to the 1979 Islamic Revolution. Spellout built a radar and communications network in the north of Iran. Peace Ruby built another air-defence network in the south and Peace Net integrated the two networks. [12] [13]
Flag of Bahrain.svg  Bahrain - Flag of the United Arab Emirates.svg  UAE
A tropo-scatter system linking Al Manamah, Bahrain to Dubai, United Arab Emirates.
Royal Air Force of Oman, Flag of Oman.svg  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, Flag of Saudi Arabia.svg  Saudi Arabia
A Royal Saudi Air Force tropo-scatter network linking major airbases and population centres in Saudi Arabia.
Yemen, Flag of Yemen.svg  Yemen
A single system linking Sana'a with Sa'dah.
BACK PORCH and IWCS, Flag of the United States.svg  United States
Two networks run by the United States linking military bases in Thailand and South Vietnam.
Phil-Tai-Oki, Flag of the Republic of China.svg  Taiwan
A system linking the Taiwan with the Philippines and Okinawa. [14]
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. [15] [16]
Japanese Troposcatter Networks, Flag of Japan.svg  Japan
Two networks linking Japanese islands from North to South.

Tactical Troposcatter Communication systems

Belarusian "Horizon" mobile tropospheric scatter communication system Milex-2019 exhibition (Minsk, Belarus) -- Vystavka Milex-2019 (Minsk, Belarus') 00010.jpg
Belarusian "Horizon" mobile tropospheric scatter communication system

As well as the permanent networks detailed above, there have been many tactical transportable systems produced by several countries: [17]

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 [18]
AN/GRC-201 Troposcatter Communication System
US Army TRC-170 Tropo Scatter Microwave System Tropo Scatter Microwave System Antenna.jpg
US Army TRC-170 Tropo Scatter Microwave System

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 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.

See also

Related Research Articles

Microwave Electromagnetic radiation with wavelengths from 1 m to 1 mm

Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF bands. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz. In all cases, microwaves include the entire SHF band at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.

Repeater Relay station

In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Some types of repeaters broadcast an identical signal, but alter its method of transmission, for example, on another frequency or baud rate.

Transmission medium Conduit for signal propagation

A transmission medium is a system or substance that can mediate the propagation of signals for the purposes of telecommunication. Signals are typically imposed on a wave of some kind suitable for the chosen medium. For example, data can modulate sound, and a transmission medium for sounds may be air, but solids and liquids may also act as the transmission medium. Vacuum or air constitutes a good transmission medium for electromagnetic waves such as light and radio waves. While material substance is not required for electromagnetic waves to propagate, such waves are usually affected by the transmission media they pass through, for instance, by absorption or reflection or refraction at the interfaces between media. Technical devices can therefore be employed to transmit or guide waves. Thus, an optical fiber or a copper cable is used as transmission media.

Radio wave Type of electromagnetic radiation

Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm ; at 30 Hz the corresponding wavelength is 10,000 km. Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a close, but slightly lower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects.

Ultra high frequency The range 300-3000 MHz of the electromagnetic spectrum

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. 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 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, and numerous other applications.

Anomalous propagation includes different forms of radio propagation due to an unusual distribution of temperature and humidity with height in the atmosphere. While this includes propagation with larger losses than in a standard atmosphere, in practical applications it is most often meant to refer to cases when signal propagates beyond normal radio horizon.

Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.

Super high frequency (SHF) is the ITU designation for radio frequencies (RF) in the range between 3 and 30 gigahertz (GHz). This band of frequencies is also known as the centimetre band or centimetre wave as the wavelengths range from one to ten centimetres. These frequencies fall within the microwave band, so radio waves with these frequencies are called microwaves. The small wavelength of microwaves allows them to be directed in narrow beams by aperture antennas such as parabolic dishes and horn antennas, so they are used for point-to-point communication and data links and for radar. This frequency range is used for most radar transmitters, wireless LANs, satellite communication, microwave radio relay links, and numerous short range terrestrial data links. They are also used for heating in industrial microwave heating, medical diathermy, microwave hyperthermy to treat cancer, and to cook food in microwave ovens.

Henryk Magnuski

Henryk Władysław Magnuski was a Polish telecommunications engineer who worked for Motorola in Chicago. He was a primary contributor in the development of one of the first Walkie-Talkie radios, the Motorola SCR-300, and influenced the company's success in the field of radio communication.

Non-line-of-sight (NLOS) radio propagation occurs outside of the typical line of sight (LOS) between the transmitter and receiver, such as in ground reflections. Near-line-of-sight conditions refer to partial obstruction by a physical object present in the innermost Fresnel zone.

White Alice Communications System US Air Force telecommunications network

The White Alice Communications System 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.

AN/TRC-97 Multiplex radio set

The AN/TRC-97 Radio Set, or TRC-97, is a radio set that has 12 multiplex channels (later expanded to 24 channels and 16 telegraph channels connected to an analog radio. The radio set is a mobile terminal that can transmit up to 40 miles straight line-of-sight at up to 1 watt, using a traveling wave tube amplifier, or 96 miles in tropospheric scatter at up to 1 kilowatt, using a tunable klystron amplifier, at a frequency range of 4.4 to 5 gigahertz and 1.2 to 2.2 gigahertz. The set has been manufactured by RCA, Camden, N.J.

Microwave transmission Transmission of information via microwaves

Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave range 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. 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.

AN/TRC-80

The AN/TRC-80 Radio Terminal Set was a United States Army communications system that provided line-of-sight or tropospheric scatter voice and teletypewriter communications between Pershing missile firing units and higher headquarters. Commonly known as the "Track 80", it was built by Collins Radio and first delivered in 1960.

Radio Technology of using radio waves to carry information

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 transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing, and other applications.

This is an index to articles about terms used in discussion of radio propagation.

Tropospheric propagation describes electromagnetic propagation in relation to the troposphere. The service area from a VHF or UHF radio transmitter extends to just beyond the optical horizon, at which point signals start to rapidly reduce in strength. Viewers living in such a "deep fringe" reception area will notice that during certain conditions, weak signals normally masked by noise increase in signal strength to allow quality reception. Such conditions are related to the current state of the troposphere.

North Atlantic Radio System

The North Atlantic Radio System (NARS) was a chain of 5 tropospheric scatter communication sites. It was an expansion of the former Distant Early Warning Line. NARS has been built for the United States Air Force (USAF) by Western Electric (AT&T) and its sites were maintained under contract by ITT Federal Electric Corporation. All NARS stations were supervised and controlled by the USAF, by agreement with the Canadian and Danish Governments.

Pole Vault (communications system) First operational troposcatter 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.

References

Citations

  1. Telecommunications: Glossary of Telecommunication Terms - tropospheric scatter (pdf) (Technical report). National Telecommunications and Information Administration. 23 August 2000. p. T-21. FED-STD-1037C. Archived (PDF) from the original on 25 December 2016. Retrieved 13 July 2021.
  2. 1 2 3 Stecker 1960.
  3. Price, Jay (10 August 2008). "Mysterious Cold War bunker closes" . Home & Garden. Charlotte Observer . The McClatchy Company. ISSN   2331-7221. OCLC   9554626. Archived from the original on 6 October 2020. Retrieved 15 July 2021. Although AT&T had dozens of similar communications bunkers across the country, the one in Chatham was part of a heavily armored and heavily guarded group of just five that went by the deceptively bland name of "Project Offices," said Albert LaFrance, who runs two Web sites dedicated to Cold War infrastructure. Unlike the more common AT&T communications bunkers, the Project Offices were apparently designed to shelter high-level government and military officials as part of a plan to preserve at least a skeletal national government in the event of a nuclear attack, LaFrance said. These “Continuance of Government” facilities would need communications capability, but communications wasn't their main mission, he said.
  4. Elliston, Jon (December 13, 2000). "Big Hole, Deep Secret". Indy Week . Retrieved March 8, 2017.
  5. coldwar-c4i.net
  6. indyweek.com (Archived copy)
  7. coldwar-c4i.net
  8. Elkins, Walter. "European Tropospheric Scatter - Army". USARMYGERMANY.com. Retrieved 15 July 2021. A major segment of the Department of Defense communications network in Europe was activated July 19 (1966). The new system went into operation as part of the ET-A ( European Tropo-Army ) network that spans a number of nations in Western Europe. The system ties in communications from Leghorn, Italy, through the Italian Alps to Bremerhaven, Germany, and from Heidelberg to within a few miles of Paris, adding more than 1,200 channel miles to the US Army Strategic Communications Command’s world-wide communications complex.
  9. Elkins, Walter. "Air Force Communications in Europe". USARMYGERMANY.com. Retrieved 15 July 2021.
  10. "A dead Dragon, or the remains of Sever TRRL". Russian Urban Exploration. n.d. Archived from the original on 4 March 2021. Sever tropospheric-scatter radio relay line (TRRL Sever) is a former Soviet communications line system designed for establishing communication with the remote regions of the country. The line was 13200 km (8200 miles) long and consisted of 46 tropospheric radio relay stations (TRRS) located mostly along the coasts of the Arctic and the Pacific oceans and major Siberian rivers: the Ob, the Enisey and the Lena.
  11. AF Net
  12. "Air Defense Command And Radars". Imperial Iranian Air Force. Archived from the original on 15 March 2012. Retrieved 15 May 2021.
  13. Clark, Jay; Salute, Joe. "The Philco-Ford Peace Ruby Project". exreps.com. Archived from the original on 16 March 2012. Retrieved 15 May 2021. The Peace Ruby program added AC&W radar sites and communications to the south of Iran, it supplemented the Spellout system to the north which provided radar coverage along the Russian boarder from Mashad to Tabriz. A later project, Peace Net, fully integreted these two systems into a state of the art air control and defense system.
  14. Farrow, J. E.; Hause, L. G. (1 January 1981). "3.3 Aspects of Equipment Covered". Recommendations for Digital Radio Common Tactical/Long-Haul Standards (Technical report). Vol. 60. United States Department of Commerce. p. 29. ASIN   B003HGFY0K. OCLC   605998563. OL   14852853M. NTIA Report 81-74. Retrieved 15 July 2021 via Google Books. Failures of the antenna, antenna mounts, or transmission lines have been observed to contribute a major portion of system unavailability. Such outages have been observed on the Scope Com system in Germany, the ETA system in Germany, the Phil-Tai-Oki system in Taiwan and most recently, on the DEB Phase I in Italy.
  15. Burton, William (19 September 2016). "Cable & Wireless in Barbados". BajanThings. Archived from the original on 18 April 2018. Retrieved 15 July 2021. 1960 – Tropospheric scatter radio link established between Barbados and Trinidad. 1965 – Tropospheric scatter system extended south to Guyana via Trinidad and North to Tortola via St. Lucia and Antigua.
  16. Stamp of Guyana (1968)
  17. Kopp, Carlo (1 August 2010). Tropospheric Scatter Communications Systems (html) (Technical report). Air Power Australia. APA-TR-2010-0801. Archived from the original on 6 May 2021. Retrieved 13 July 2021.
  18. Williamson, John, ed. (27 January 2011). "Terrestrial microwave and tropospheric scatter - AN/TRC-170(V) tactical digital tropospheric scatter radio (United States)". Jane's Military Communications (32nd ed.). Janes Information Group. ISBN   978-0710629487. OCLC   751723522. Archived from the original on 5 February 2011. Retrieved 13 July 2021.

Bibliography