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.
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.
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, 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 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 RCA 474L Ballistic Missile Early Warning System was a United States Air Force Cold War early warning radar, computer, and communications system, for ballistic missile detection. The network of twelve radars, which was constructed beginning in 1958 and became operational in 1961, was built to detect a mass ballistic missile attack launched on northern approaches [for] 15 to 25 minutes' warning time also provided Project Space Track satellite data.
Naval Air Station Keflavik (NASKEF) is a United States Navy air station at Keflavík International Airport, Iceland, located on the Reykjanes peninsula on the south-west portion of the island. NASKEF was closed on 8 September 2006, and its facilities were taken over by the Icelandic Defence Agency as their primary base until 1 January 2011, when the Agency was abolished and the base handed over to the Icelandic Coast Guard, which has operated the base until 2017. US forces returned to Keflavik in 2016, renovating parts of the base to accommodate P-8As on short duration/expeditionary detachments.
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.
Canadian Forces Station Saglek is a Royal Canadian Air Force radar base in the former Pinetree Line and currently part of the North Warning System, located near Saglek Bay in Newfoundland and Labrador, 367.7 miles (591.8 km) north-northwest of CFB Goose Bay.
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.
Canadian Forces Station Ramore is a closed General Surveillance Radar station. It is located 4 miles (6.4 km) east of Ramore, Ontario. It was closed in 1974. It was operated as part of the Pinetree Line network controlled by NORAD. It has since been sold and is now private property.
Hofn Air Station is a closed United States Air Force General Surveillance Radar station. It is located 231.4 miles (372.4 km) east of Naval Air Station Keflavik, Iceland. It was closed on 30 June 1992.
Langanes Air Station is a closed United States Air Force General Surveillance Radar station. It is located 265 miles (426 km) northeast of Naval Air Station Keflavik, Iceland. The new station (H-2A) was closed on 28 June 2006 as part of the closure of United States military facilities in Iceland.
Cold Bay Air Force Station is a closed United States Air Force General Surveillance Radar station. It is located 625 miles (1,006 km) southwest of Anchorage, Alaska.
DYE Stations were Distant Early Warning Line sites of the DEW Line eastern extension in Arctic North America in Greenland and Iceland. DYE Stations were equipped with the 600 MHz AN/FPS-30 long-range radar within geodesic domes of about 60 feet diameter. Crews were regularly supplied and rotated by C-130 aircraft of the 109th Airlift Wing (NYANG) staging through Sondrestrom Air Base.
Mid-Canada Line Site 070 Kempis was a part of the Mid-Canada Line air defence network. During the late 1950s, the Mid-Canada Line (MCL) was developed as a secondary line of detection in case enemy aircraft penetrated the Distant Early Warning Line. This consisted of approximately 90 unmanned sites and eight Sector Control Stations located along the 55th parallel. Each site sent out a radio beam to its neighbouring site. If an aircraft interrupted the beam, an intruder alarm would sound.
Mid-Canada Line Site 050 Fort Albany was a part of the Mid-Canada Line air defence network. During the late 1950s, the Mid-Canada Line (MCL) was developed as a secondary line of detection in case enemy aircraft penetrated the Distant Early Warning Line. This consisted of approximately 90 unmanned sites and eight Sector Control Stations located along the 55th parallel. Each site sent out a radio beam to its neighbouring site. If an aircraft interrupted the beam, an intruder alarm would sound.
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.
RAF Ringstead is a former Royal Air Force radar station at Ringstead Bay, Dorset, England. It is notable for having served three separate functions: first as a Chain Home early-warning radar station during WWII and then, during the Cold War, as a Rotor station and then, finally, as a USAF Tropospheric scatter station. The first of these functions commenced in 1942; the last of the functions ceased in 1974. The structural remains were Grade II listed in 2020.
