132-570: ROTOR was an elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bombers . To get it operational as quickly as possible, it was initially made up primarily of WWII-era systems, notably the original Chain Home radars for the early warning role, and the AMES Type 7 for plotting and interception control. Data from these stations
264-466: A fractal surface, such as rocks or soil, and are used by navigation radars. A radar beam follows a linear path in vacuum but follows a somewhat curved path in atmosphere due to variation in the refractive index of air, which is called the radar horizon . Even when the beam is emitted parallel to the ground, the beam rises above the ground as the curvature of the Earth sinks below the horizon. Furthermore,
396-404: A transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna , a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving information about
528-424: A transmitter that emits radio waves known as radar signals in predetermined directions. When these signals contact an object they are usually reflected or scattered in many directions, although some of them will be absorbed and penetrate into the target. Radar signals are reflected especially well by materials of considerable electrical conductivity —such as most metals, seawater , and wet ground. This makes
660-512: A ROTOR bunker was constructed above ground to allow equipment to be tested in an operational environment. The building, locally designated as H Building, originally incorporated a replica of the sector operations centre at RAF Bawburgh. The building was demolished June 2020. RAF Staxton Wold is the only Chain Home site still used as a military radar site but with no remains of the CH station on site after being rebuilt for Linesman/Mediator in 1964. Today it
792-474: A bridge. They also cut off the electricity relied on by Berlin, using their control over the generating plants in the Soviet zone. Surface traffic from non-Soviet zones to Berlin was blockaded, leaving open only the air corridors. The Soviets rejected arguments that the occupation rights in the non-Soviet sectors of Berlin and the use of the supply routes during the previous three years had given Britain, France and
924-840: A common noun, losing all capitalization . The modern uses of radar are highly diverse, including air and terrestrial traffic control, radar astronomy , air-defense systems , anti-missile systems , marine radars to locate landmarks and other ships, aircraft anti-collision systems, ocean surveillance systems, outer space surveillance and rendezvous systems, meteorological precipitation monitoring, radar remote sensing , altimetry and flight control systems , guided missile target locating systems, self-driving cars , and ground-penetrating radar for geological observations. Modern high tech radar systems use digital signal processing and machine learning and are capable of extracting useful information from very high noise levels. Other systems which are similar to radar make use of other parts of
1056-472: A damaging impact on East Germany, as the drying up of coal and steel shipments seriously hindered industrial development in the Soviet zone. On 25 June, the Soviets stopped supplying food to the civilian population in the non-Soviet sectors of Berlin. Motor traffic from Berlin to the western zones was permitted, but this required a 23-kilometre (14 mi) detour to a ferry crossing because of alleged "repairs" to
1188-660: A day. The RAF was somewhat better prepared, since it had already moved some aircraft into the German area, and they expected to be able to supply about 400 tons a day. This was not nearly enough to move the approximately 5,000 total tons a day that would be needed, but these numbers could be increased as new aircraft arrived from the United Kingdom, the United States, and France. The RAF would be relied on to increase its numbers quickly. It could fly additional aircraft in from Britain in
1320-482: A different dielectric constant or diamagnetic constant from the first, the waves will reflect or scatter from the boundary between the materials. This means that a solid object in air or in a vacuum , or a significant change in atomic density between the object and what is surrounding it, will usually scatter radar (radio) waves from its surface. This is particularly true for electrically conductive materials such as metal and carbon fibre, making radar well-suited to
1452-438: A force of tanks and trucks, the Soviets could not claim that cargo aircraft were a military threat. The airlift option critically depended on scale and effectiveness. If the supplies could not be flown in fast enough, Soviet help would eventually be needed to prevent starvation. Clay was told to take advice from General LeMay to see if an airlift was possible. "We can haul anything," LeMay responded, after initially taken aback by
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#17328516931721584-535: A full radar system, that he called a telemobiloscope . It operated on a 50 cm wavelength and the pulsed radar signal was created via a spark-gap. His system already used the classic antenna setup of horn antenna with parabolic reflector and was presented to German military officials in practical tests in Cologne and Rotterdam harbour but was rejected. In 1915, Robert Watson-Watt used radio technology to provide advance warning of thunderstorms to airmen and during
1716-729: A physics instructor at the Imperial Russian Navy school in Kronstadt , developed an apparatus using a coherer tube for detecting distant lightning strikes. The next year, he added a spark-gap transmitter . In 1897, while testing this equipment for communicating between two ships in the Baltic Sea , he took note of an interference beat caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, but he did nothing more with this observation. The German inventor Christian Hülsmeyer
1848-495: A proposal for further intensive research on radio-echo signals from moving targets to take place at NRL, where Taylor and Young were based at the time. Similarly, in the UK, L. S. Alder took out a secret provisional patent for Naval radar in 1928. W.A.S. Butement and P. E. Pollard developed a breadboard test unit, operating at 50 cm (600 MHz) and using pulsed modulation which gave successful laboratory results. In January 1931,
1980-698: A pulsed system, and the first such elementary apparatus was demonstrated in December 1934 by the American Robert M. Page , working at the Naval Research Laboratory . The following year, the United States Army successfully tested a primitive surface-to-surface radar to aim coastal battery searchlights at night. This design was followed by a pulsed system demonstrated in May 1935 by Rudolf Kühnhold and
2112-442: A rescue. For similar reasons, objects intended to avoid detection will not have inside corners or surfaces and edges perpendicular to likely detection directions, which leads to "odd" looking stealth aircraft . These precautions do not totally eliminate reflection because of diffraction , especially at longer wavelengths. Half wavelength long wires or strips of conducting material, such as chaff , are very reflective but do not direct
2244-622: A result of the introduction of the Type 80, many of the existing ROTOR sites were rationalized into Master Radar Stations (MRS), while the rest were made redundant, some only two years after opening. During the same period, the introduction of the first surface-to-air missiles rendered the anti-aircraft guns obsolete, and the Army handed the air defence mission entirely to the RAF. All of the AAOR sites were closed. A few of
2376-569: A single hop, bringing the RAF fleet to about 150 Dakotas and 40 of the larger Avro Yorks with a 10-ton payload . With this fleet, the British contribution was expected to rise to 750 tons a day in the short term, albeit at the cost of suspending all air traffic except for the airlift to Berlin. For a longer-term operation, the US would have to add additional aircraft as soon as possible, and those would have to be as large as possible while still able to fly into
2508-621: A strong, allied Germany to assist in the rebuilding of the West European economy. To coordinate the economies of the British and United States occupation zones, these were combined on 1 January 1947 into what was referred to as the Bizone (renamed the Trizone when France joined on 1 August 1948). After March 1946 the British zonal advisory board ( Zonenbeirat ) was established, with representatives of
2640-481: A successful sneak attack by missiles. Such a system did not require a large number of radars nor country-wide coverage. To reduce the cost of this much smaller network, studies on integrating the military radars with civilian air traffic control led to the Linesman/Mediator system of only five primary stations. The original ROTOR was replaced by Linesman in stages, starting in 1967. A similar expedient system in
2772-662: A system might do, Wilkins recalled the earlier report about aircraft causing radio interference. This revelation led to the Daventry Experiment of 26 February 1935, using a powerful BBC shortwave transmitter as the source and their GPO receiver setup in a field while a bomber flew around the site. When the plane was clearly detected, Hugh Dowding , the Air Member for Supply and Research , was very impressed with their system's potential and funds were immediately provided for further operational development. Watson-Watt's team patented
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#17328516931722904-527: A time the Americans and British continued to supply the city by air as they were worried that the Soviets would resume the blockade and were only trying to disrupt western supply lines. The Berlin Airlift officially ended on 30 September 1949 after fifteen months. The US Air Force had delivered 1,783,573 tons (76.4% of total) and the RAF 541,937 tons (23.3% of total), totalling 2,334,374 tons, nearly two-thirds of which
3036-514: A wide region and direct fighter aircraft towards targets. Marine radars are used to measure the bearing and distance of ships to prevent collision with other ships, to navigate, and to fix their position at sea when within range of shore or other fixed references such as islands, buoys, and lightships. In port or in harbour, vessel traffic service radar systems are used to monitor and regulate ship movements in busy waters. Meteorologists use radar to monitor precipitation and wind. It has become
3168-751: A writeup on the apparatus was entered in the Inventions Book maintained by the Royal Engineers. This is the first official record in Great Britain of the technology that was used in coastal defence and was incorporated into Chain Home as Chain Home (low) . Before the Second World War , researchers in the United Kingdom, France , Germany , Italy , Japan , the Netherlands , the Soviet Union , and
3300-452: Is a simplification for transmission in a vacuum without interference. The propagation factor accounts for the effects of multipath and shadowing and depends on the details of the environment. In a real-world situation, pathloss effects are also considered. Frequency shift is caused by motion that changes the number of wavelengths between the reflector and the radar. This can degrade or enhance radar performance depending upon how it affects
3432-451: Is as follows, where F D {\displaystyle F_{D}} is Doppler frequency, F T {\displaystyle F_{T}} is transmit frequency, V R {\displaystyle V_{R}} is radial velocity, and C {\displaystyle C} is the speed of light: Passive radar is applicable to electronic countermeasures and radio astronomy as follows: Only
3564-560: Is intended. Radar relies on its own transmissions rather than light from the Sun or the Moon, or from electromagnetic waves emitted by the target objects themselves, such as infrared radiation (heat). This process of directing artificial radio waves towards objects is called illumination , although radio waves are invisible to the human eye as well as optical cameras. If electromagnetic waves travelling through one material meet another material, having
3696-705: Is no practicability in maintaining our position in Berlin and it must not be evaluated on that basis... We are convinced that our remaining in Berlin is essential to our prestige in Germany and in Europe. Whether for good or bad, it has become a symbol of the American intent. Believing that Britain, France, and the United States had little option other than to acquiesce, the Soviet Military Administration in Germany celebrated
3828-583: Is the former home of an RAF TPS 77 RRH (remote radar head). RAF Boulmer is a working RAF building, which is housed in an ex-"ROTOR" R3 RAF Boulmer ('EZS') GCI R3 ROTOR Radar Station & Control and Reporting Centre in the UK Air Surveillance and Control System. In terms of current condition, the ROTOR sites vary from demolished to intact. For example, West Myne in Somerset was the last ROTOR 3 CHEL site. It
3960-417: Is the range. This yields: This shows that the received power declines as the fourth power of the range, which means that the received power from distant targets is relatively very small. Additional filtering and pulse integration modifies the radar equation slightly for pulse-Doppler radar performance , which can be used to increase detection range and reduce transmit power. The equation above with F = 1
4092-568: The Air Ministry felt there was no point introducing new radars that would likely become obsolete in a few years. They planned to allow radar to continue developing through this period and use the existing WWII-era systems in the meantime. To consider the issue in more depth, the Cherry Report was commissioned in 1945. This report noted that the increasing speeds of new bombers, and especially future designs that were jet-powered, would travel across
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4224-702: The Benelux nations, met twice in London ( London 6-Power Conference ) in the first half of 1948 to discuss the future of Germany, going ahead despite Soviet threats to ignore any resulting decisions. Eventually the London Agreement on German External Debts , also known as the London Debt Agreement ( Londoner Schuldenabkommen ), was concluded. Under the London Debts Agreement of 1953, the repayable amount
4356-591: The Deutsche Mark would be introduced, but the Soviets refused to permit its use as legal tender in Berlin. The Allies had already transported 250,000,000 Deutsche marks into the city and it quickly became the standard currency in all four sectors. The day after the 18 June 1948 announcement of the new Deutsche Mark , Soviet guards halted all passenger trains and traffic on the autobahn to Berlin, delayed Western and German freight shipments and required that all water transport secure special Soviet permission. On 21 June,
4488-623: The Nyquist frequency , since the returned frequency otherwise cannot be distinguished from shifting of a harmonic frequency above or below, thus requiring: Or when substituting with F D {\displaystyle F_{D}} : As an example, a Doppler weather radar with a pulse rate of 2 kHz and transmit frequency of 1 GHz can reliably measure weather speed up to at most 150 m/s (340 mph), thus cannot reliably determine radial velocity of aircraft moving 1,000 m/s (2,200 mph). In all electromagnetic radiation ,
4620-640: The Oder-Neisse line , into four temporary occupation zones each one controlled by one of the four occupying Allied powers : the United States, the United Kingdom, France and the Soviet Union (thus re-affirming principles laid out earlier by the Yalta Conference ). These zones were located roughly around the then-current locations of the allied armies. As the seat of the Allied Control Council , Berlin
4752-714: The RAF's Pathfinder . The information provided by radar includes the bearing and range (and therefore position) of the object from the radar scanner. It is thus used in many different fields where the need for such positioning is crucial. The first use of radar was for military purposes: to locate air, ground and sea targets. This evolved in the civilian field into applications for aircraft, ships, and automobiles. In aviation , aircraft can be equipped with radar devices that warn of aircraft or other obstacles in or approaching their path, display weather information, and give accurate altitude readings. The first commercial device fitted to aircraft
4884-482: The Socialist Unity Party ("SED") , claiming at the time that it would not have a Marxist–Leninist or Soviet orientation. The SED leaders then called for the "establishment of an anti-fascist, democratic regime, a parliamentary democratic republic" while the Soviet Military Administration suppressed all other political activities. Factories, equipment, technicians, managers and skilled personnel were removed to
5016-659: The Soviet Union blocked the Western Allies ' railway, road, and canal access to the sectors of Berlin under Western control . The Soviets offered to drop the blockade if the Western Allies withdrew the newly introduced Deutsche Mark from West Berlin . The Western Allies organised the Berlin Airlift (German: Berliner Luftbrücke , lit. "Berlin Air Bridge") from 26 June 1948 to 30 September 1949 to carry supplies to
5148-440: The electromagnetic spectrum . One example is lidar , which uses predominantly infrared light from lasers rather than radio waves. With the emergence of driverless vehicles, radar is expected to assist the automated platform to monitor its environment, thus preventing unwanted incidents. As early as 1886, German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. In 1895, Alexander Popov ,
5280-407: The reflective surfaces . A corner reflector consists of three flat surfaces meeting like the inside corner of a cube. The structure will reflect waves entering its opening directly back to the source. They are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect. Corner reflectors on boats, for example, make them more detectable to avoid collision or during
5412-527: The "new boy" Arnold Frederic Wilkins to conduct an extensive review of available shortwave units. Wilkins would select a General Post Office model after noting its manual's description of a "fading" effect (the common term for interference at the time) when aircraft flew overhead. By placing a transmitter and receiver on opposite sides of the Potomac River in 1922, U.S. Navy researchers A. Hoyt Taylor and Leo C. Young discovered that ships passing through
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5544-414: The 'R' series (R1, R2, R3 and R4 etc.), while those on the western side of the UK were generally semi-sunken hardened structures ('R6') or above ground 'Secco' type huts (Hartland Point etc.). The R-series bunkers themselves were otherwise similar, featuring 10-foot-thick (3.0 m) concrete walls with all equipment, operations generators and air conditioning located inside. Additionally, ROTOR re-arranged
5676-413: The 1920s went on to lead the U.K. research establishment to make many advances using radio techniques, including the probing of the ionosphere and the detection of lightning at long distances. Through his lightning experiments, Watson-Watt became an expert on the use of radio direction finding before turning his inquiry to shortwave transmission. Requiring a suitable receiver for such studies, he told
5808-605: The 98,000 American troops in West Germany in March 1948, only 31,000 were combat forces, and only one reserve division was immediately available in the United States. Soviet military forces in the Soviet sector that surrounded Berlin totaled 1.5 million. The two United States regiments in Berlin could have provided little resistance against a Soviet attack. Because of the imbalance, US war plans were based on using hundreds of atomic bombs, but only about 50 Fat Man -specification bombs,
5940-484: The Americans and British were greatly outnumbered because of the postwar scaling back of their armies. The United States, like other Western countries, had disbanded most of its troops and was largely inferior in the European theatre. The entire United States Army had been reduced to 552,000 men by February 1948. Military forces in the western sectors of Berlin numbered only 8,973 Americans, 7,606 British and 6,100 French. Of
6072-588: The Berlin airports. Only one aircraft type was suitable, the four-engined C-54 Skymaster and its US Navy equivalent, the R5D, of which the US military had approximately 565, with 268 Air Force and Navy Skymasters in MATS , 168 in the troop carrier groups, and 80 Navy R5Ds in miscellaneous commands. Planners calculated that including C-54s already ordered to Germany and drawing on those flying with civilian carriers, 447 Skymasters could be available for an "extreme emergency". Given
6204-561: The Eastern zone must withdraw, thus preventing the use of navigation beacons to mark air routes. On 20 April, the Soviets demanded that all barges obtain clearance before entering the Soviet zone. Creation of an economically stable western Germany required reform of the unstable Reichsmark German currency introduced after the 1920s German inflation . The Soviets continued the debasing of the Reichsmark, which had undergone severe inflation during
6336-515: The Foreness, Kent station which grid ref is TR 385710 Radar Radar is a system that uses radio waves to determine the distance ( ranging ), direction ( azimuth and elevation angles ), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track aircraft , ships , spacecraft , guided missiles , motor vehicles , map weather formations , and terrain . A radar system consists of
6468-670: The ROTOR and AAOR stations were re-used for Regional Seats of Government or local authority wartime headquarters. Until the end of the Cold War , many of the sites were retained by the government. They were later sold to private buyers, converted into museums (for example Hack Green ) or transferred to the National Air Traffic Control Centre . At the Radar Research Establishment in Malvern, Worcestershire
6600-524: The Soviet Union. In a June 1945 meeting, Stalin informed German communist leaders that he expected to slowly undermine the British position within their occupation zone, that the United States would withdraw within a year or two and that nothing would then stand in the way of a united Germany under communist control within the Soviet orbit. Stalin and other leaders told visiting Bulgarian and Yugoslavian delegations in early 1946 that Germany must be both Soviet and communist. A further factor contributing to
6732-526: The Soviet Union. In response, the Soviets started a public relations campaign against American policy and began to obstruct the administrative work of all four zones of occupation. Until the blockade began in 1948, the Truman Administration had not decided whether American forces should remain in West Berlin after the establishment of a West German government, planned for 1949. Berlin quickly became
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#17328516931726864-462: The Soviets and the other allied powers. Internal Soviet reports in April stated that "Our control and restrictive measures have dealt a strong blow to the prestige of the Americans and British in Germany" and that the Americans have "admitted" that the idea of an airlift would be too expensive. On 9 April, Soviet officials demanded that American military personnel maintaining communication equipment in
6996-507: The Sun . British transports, including Handley Page Haltons and Short Sunderlands , flew as well. At the height of the airlift, one plane reached West Berlin every thirty seconds. Seventeen American and eight British aircraft crashed during the operation. A total of 101 fatalities were recorded as a result of the operation, including 40 Britons and 31 Americans , mostly due to non-flying accidents. The Berlin Blockade served to highlight
7128-410: The United States a legal claim to use of the highways, tunnels, railroads, and canals. Relying on Soviet goodwill after the war, Britain, France, and the United States had never negotiated an agreement with the Soviets to guarantee these land-based rights of access to Berlin through the Soviet zone. At the time, West Berlin had an estimated 36 days worth of food, and 45 days worth of coal. Militarily,
7260-465: The United States was the Lashup Radar Network . As the threat of German air attack became ever more remote, UK radar operations were wound down late in the war, and by the time the war ended were already largely unused. When the war ended, there was a general feeling that another war was at least ten years in the future. Given the rapid ongoing improvements in radar systems through this period,
7392-714: The United States, independently and in great secrecy, developed technologies that led to the modern version of radar. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain's radar development, Hungary and Sweden generated its radar technology during the war. In France in 1934, following systematic studies on the split-anode magnetron , the research branch of the Compagnie générale de la télégraphie sans fil (CSF) headed by Maurice Ponte with Henri Gutton, Sylvain Berline and M. Hugon, began developing an obstacle-locating radio apparatus, aspects of which were installed on
7524-533: The arrest of Oshchepkov and his subsequent gulag sentence. In total, only 607 Redut stations were produced during the war. The first Russian airborne radar, Gneiss-2 , entered into service in June 1943 on Pe-2 dive bombers. More than 230 Gneiss-2 stations were produced by the end of 1944. The French and Soviet systems, however, featured continuous-wave operation that did not provide the full performance ultimately synonymous with modern radar systems. Full radar evolved as
7656-475: The beam path caused the received signal to fade in and out. Taylor submitted a report, suggesting that this phenomenon might be used to detect the presence of ships in low visibility, but the Navy did not immediately continue the work. Eight years later, Lawrence A. Hyland at the Naval Research Laboratory (NRL) observed similar fading effects from passing aircraft; this revelation led to a patent application as well as
7788-565: The beginning of the blockade. General Clay felt that the Soviets were bluffing about Berlin since they would not want to be viewed as starting a Third World War . He believed that Stalin did not want a war and that Soviet actions were aimed at exerting military and political pressure on the West to obtain concessions, relying on the West's prudence and unwillingness to provoke a war. General Curtis LeMay , commander of United States Air Forces in Europe (USAFE), reportedly favored an aggressive response to
7920-431: The blockade was that there had never been a formal agreement guaranteeing rail and road access to Berlin through the Soviet zone. At the end of the war, western leaders had relied on Soviet goodwill to provide them with access. At that time, the western allies assumed that the Soviets' refusal to grant any cargo access other than one rail line, limited to ten trains per day, was temporary, but the Soviets refused expansion to
8052-413: The blockade, in which his B-29s with fighter escort would approach Soviet air bases while ground troops attempted to reach Berlin; Washington vetoed the plan. Although the ground routes had never been negotiated, the same was not true of the air. On 30 November 1945, it had been agreed in writing that there would be three twenty-mile-wide air corridors providing free access to Berlin. Additionally, unlike
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#17328516931728184-472: The circulation in Berlin exclusively of the currency of the Soviet occupation zone." The Soviets launched a massive propaganda campaign condemning Britain, the United States and France by radio, newspaper and loudspeaker. The Soviets conducted well-advertised military maneuvers just outside the city. Rumors of a potential occupation by Soviet troops spread quickly. German communists demonstrated, rioted and attacked pro-West German leaders attending meetings for
8316-489: The command and control systems. The introduction of the carcinotron radar jammer in the mid-1950s was a serious blow to these plans; a single aircraft carrying a carcinotron could jam the ROTOR radars so completely that they were rendered useless. At the same time, the introduction of the hydrogen bomb and ballistic missile greatly changed the nature of the strategic threat, and the idea of whole-country defence became untenable. The only way to defend against missile attacks
8448-542: The competing ideological and economic visions for postwar Europe. It played a major role in aligning West Berlin with the United States and Britain as the major protecting powers, and in drawing West Germany into the NATO orbit several years later in 1955. From 17 July to 2 August 1945, the victorious Allies reached the Potsdam Agreement on the fate of postwar Europe, calling for the division of defeated Germany, west of
8580-636: The crisis broke out. He had been the commander of the US China Burma India Theater in 1944–45 and he had a detailed knowledge of the previously largest airlift—the World War II American airlift from India over the Hump of the Himalayas to China. His endorsement of the airlift option gave it a major boost. The British and Americans agreed to start a joint operation without delay; the US action
8712-576: The day the Deutsche Mark was introduced, the Soviet military halted a United States military supply train to Berlin and sent it back to western Germany. On 22 June, the Soviets announced that they would introduce the East German mark in their zone. That same day, a Soviet representative told the other three occupying powers that "We are warning both you and the population of Berlin that we shall apply economic and administrative sanctions that will lead to
8844-408: The detection of aircraft and ships. Radar absorbing material , containing resistive and sometimes magnetic substances, is used on military vehicles to reduce radar reflection . This is the radio equivalent of painting something a dark colour so that it cannot be seen by the eye at night. Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of
8976-421: The detection process. As an example, moving target indication can interact with Doppler to produce signal cancellation at certain radial velocities, which degrades performance. Sea-based radar systems, semi-active radar homing , active radar homing , weather radar , military aircraft, and radar astronomy rely on the Doppler effect to enhance performance. This produces information about target velocity during
9108-411: The detection process. This also allows small objects to be detected in an environment containing much larger nearby slow moving objects. Doppler shift depends upon whether the radar configuration is active or passive. Active radar transmits a signal that is reflected back to the receiver. Passive radar depends upon the object sending a signal to the receiver. The Doppler frequency shift for active radar
9240-441: The device in patent GB593017. Development of radar greatly expanded on 1 September 1936, when Watson-Watt became superintendent of a new establishment under the British Air Ministry , Bawdsey Research Station located in Bawdsey Manor , near Felixstowe, Suffolk. Work there resulted in the design and installation of aircraft detection and tracking stations called " Chain Home " along the East and South coasts of England in time for
9372-538: The electric field is perpendicular to the direction of propagation, and the electric field direction is the polarization of the wave. For a transmitted radar signal, the polarization can be controlled to yield different effects. Radars use horizontal, vertical, linear, and circular polarization to detect different types of reflections. For example, circular polarization is used to minimize the interference caused by rain. Linear polarization returns usually indicate metal surfaces. Random polarization returns usually indicate
9504-474: The entire United Kingdom. This led to the Master Radar Stations that filled both early warning and ground controlled interception roles. The original ROTOR plans for 66 radars was repeatedly reduced, ultimately only requiring half that number of stations. Many of the operations rooms, recently completed, were sold. ROTOR called for the continual upgrading of the network over time, both the radars and
9636-473: The entire area in front of it, and then used one of Watson-Watt's own radio direction finders to determine the direction of the returned echoes. This fact meant CH transmitters had to be much more powerful and have better antennas than competing systems but allowed its rapid introduction using existing technologies. A key development was the cavity magnetron in the UK, which allowed the creation of relatively small systems with sub-meter resolution. Britain shared
9768-581: The existing RAF Fighter Command structure into six "Sector Operational Commands" (SOC) with their own command bunkers (three level 'R4' protected accommodation). Only four of these were built. Additional "Anti-Aircraft Operations Rooms" were built to coordinate the British Army 's AA defences in the same overall system. The entire network of bunkers, radars, fighter control and command centres used up 350,000 tons of concrete , 20,000 tons of steel and thousands of miles of telephone and telex connections. The work
9900-529: The existing radars if they were upgraded as the Cherry Report suggested. Most of the new network would be made up of 28 rebuilt Chain Home systems, while the rest were taken from the existing selection of Chain Home Low , Chain Home Extra Low and the various Ground-controlled interception (GCI) radars. This was, in part, a stop-gap measure anticipating the availability of the dramatically improved radar, which
10032-458: The extension of the Marshall Plan to Germany, finalised the economic merger of the western occupation zones in Germany and agreed upon the establishment of a federal system of government for them. After a 9 March meeting between Stalin and his military advisers, a secret memorandum was sent to Molotov on 12 March 1948, outlining a plan to force the policy of the western allies into line with
10164-496: The feasibility assessment made by the British, an airlift appeared to be the best course of action. One remaining concern was the population of Berlin. Clay called in Ernst Reuter , the mayor-elect of Berlin, accompanied by his aide, Willy Brandt . Clay told Reuter: Look, I am ready to try an airlift. I can't guarantee it will work. I am sure that even at its best, people are going to be cold and people are going to be hungry. And if
10296-411: The firm GEMA [ de ] in Germany and then another in June 1935 by an Air Ministry team led by Robert Watson-Watt in Great Britain. In 1935, Watson-Watt was asked to judge recent reports of a German radio-based death ray and turned the request over to Wilkins. Wilkins returned a set of calculations demonstrating the system was basically impossible. When Watson-Watt then asked what such
10428-427: The focal point of both US and Soviet efforts to re-align Europe to their respective visions. As Soviet Foreign Minister Vyacheslav Molotov noted, "What happens to Berlin, happens to Germany; what happens to Germany, happens to Europe." Berlin had suffered enormous damage; its prewar population of 4.3 million people was reduced to 2.8 million. After harsh treatment, forced emigration, political repression and
10560-410: The four-power control machinery had become unworkable. For the city of Berlin, however, this was an indication for a major crisis. On 25 March 1948, the Soviets issued orders restricting Western military and passenger traffic between the American, British and French occupation zones and Berlin. These new measures began on 1 April along with an announcement that no cargo could leave Berlin by rail without
10692-464: The inquiry, "Can you haul coal?" When American forces consulted Britain's Royal Air Force about a possible joint airlift, they learned the RAF was already running an airlift in support of British troops in Berlin. General Clay's counterpart, General Sir Brian Robertson , was ready with some concrete numbers. During the Little Lift in April 1948, British Air Commodore Reginald Waite had calculated
10824-415: The municipal government in the Soviet sector. On 24 June, the Soviets severed land and water connections between the non-Soviet zones and Berlin. That same day, they halted all rail and barge traffic in and out of Berlin. The West answered by introducing a counter-blockade, stopping all rail traffic into East Germany from the British and US zones. Over the following months, this counter-blockade would have
10956-400: The name AMES Type 80 , began in 1954 with the first systems declared operational the next year. As installations continued, it was found that the accuracy was such that it could also be used to direct the interceptors, with no need to forward the information to the ROTOR control centres. By concentrating all of the plotting at a single site the total number of operators was greatly reduced. As
11088-425: The next 75 days, while the United States continued supplying its military forces by using cargo aircraft. Some 20 flights a day continued through June, building up stocks of food against future Soviet actions, so that by the time the blockade began at the end of June, at least 18 days' supply per major food type, and in some types, much more, had been stockpiled that provided time to build up the ensuing airlift. At
11220-623: The objects' locations and speeds. Radar was developed secretly for military use by several countries in the period before and during World War II . A key development was the cavity magnetron in the United Kingdom , which allowed the creation of relatively small systems with sub-meter resolution. The term RADAR was coined in 1940 by the United States Navy as an acronym for "radio detection and ranging". The term radar has since entered English and other languages as an anacronym ,
11352-494: The ocean liner Normandie in 1935. During the same period, Soviet military engineer P.K. Oshchepkov , in collaboration with the Leningrad Electrotechnical Institute , produced an experimental apparatus, RAPID, capable of detecting an aircraft within 3 km of a receiver. The Soviets produced their first mass production radars RUS-1 and RUS-2 Redut in 1939 but further development was slowed following
11484-456: The only version available to the US military, existed in mid-1948. In March 1948, only 35 " Silverplate " atomic-capable Boeing B-29 Superfortress bombers—just over half of the 65 Silverplate specification B-29 aircraft built through the end of 1947—and a few trained flight and assembly crews were available. Three B-29 groups arrived in Europe in July and August 1948. Despite the intention to signal
11616-520: The outbreak of World War II in 1939. This system provided the vital advance information that helped the Royal Air Force win the Battle of Britain ; without it, significant numbers of fighter aircraft, which Great Britain did not have available, would always have needed to be in the air to respond quickly. The radar formed part of the " Dowding system " for collecting reports of enemy aircraft and coordinating
11748-589: The over two million people of Berlin. Additionally, for heat and power, 3,475 tons of coal, diesel and petrol were also required daily. The postwar demobilisation left the US forces in Europe with only two groups of C-47 Skytrain transports (the military version of the Douglas DC-3 , which the British called the "Dakota"), nominally 96 aircraft, each of which could carry about 3.5 tons of cargo. LeMay believed that "with an all-out effort" of 100 daily round trips these would be able to haul about 300 tons of supplies
11880-461: The particularly harsh winter of 1945–1946, Germans in the Soviet-controlled zone were hostile to Soviet endeavours. Local elections in 1946 resulted in a massive anti-communist protest vote, especially in the Soviet sector of Berlin. Berlin's citizens overwhelmingly elected non-Communist members to its city government. American planners had privately decided during the war that it would need
12012-520: The people of Berlin won't stand that, it will fail. And I don't want to go into this unless I have your assurance that the people will be heavily in approval. Reuter, although skeptical, assured Clay that Berlin would make all the necessary sacrifices and that the Berliners would support his actions. General Albert Wedemeyer , the US Army chief of plans and operations, was in Europe on an inspection tour when
12144-408: The people of West Berlin, a difficult feat given the size of the city and the population. American and British air forces flew over Berlin more than 250,000 times, dropping necessities such as fuel and food, with the original plan being to lift 3,475 tons of supplies daily. By the spring of 1949, that number was often met twofold, with the peak daily delivery totalling 12,941 tons . Among these
12276-438: The permission of the Soviet commander. Each train and truck was to be searched by the Soviet authorities. On 2 April, General Clay ordered a halt to all military trains and required that supplies to the military garrison be transported by air, in what was dubbed the "Little Lift." The Soviets eased their restrictions on Allied military trains on 10 April 1948, but continued periodically to interrupt rail and road traffic during
12408-415: The plotting boards of the existing Dowding system so rapidly that they would fly off the maps before the interception could be arranged. The report suggested that a radar with 250 miles (400 km) range would be needed to replace the existing AMES Type 7/GCI systems, which were limited to about 90 miles (140 km) against bomber-sized targets. Estimating that such a radar would be available around 1957,
12540-706: The primary tool for short-term weather forecasting and watching for severe weather such as thunderstorms , tornadoes , winter storms , precipitation types, etc. Geologists use specialized ground-penetrating radars to map the composition of Earth's crust . Police forces use radar guns to monitor vehicle speeds on the roads. Automotive radars are used for adaptive cruise control and emergency breaking on vehicles by ignoring stationary roadside objects that could cause incorrect brake application and instead measuring moving objects to prevent collision with other vehicles. As part of Intelligent Transport Systems , fixed-position stopped vehicle detection (SVD) radars are mounted on
12672-432: The radial component of the velocity is relevant. When the reflector is moving at right angle to the radar beam, it has no relative velocity. Objects moving parallel to the radar beam produce the maximum Doppler frequency shift. When the transmit frequency ( F T {\displaystyle F_{T}} ) is pulsed, using a pulse repeat frequency of F R {\displaystyle F_{R}} ,
12804-445: The report suggested that existing GCI stations should receive upgraded antennas with more accuracy, new electronics for better performance, upgrades to their display systems, four Type 13's for height measuring, and two Type 14 units for anti-jamming use. Additionally, their information would be sent to six new command centres, who would produce much larger maps of the airspace, up to 1,000 miles (1,600 km) across. Additionally, all of
12936-576: The resources required to support the entire city. Based on a minimum daily ration of 1,990 kilocalories (July 1948), the American military government set a total of daily supplies needed at 646 tons of flour and wheat, 125 tons of cereal, 64 tons of fat, 109 tons of meat and fish, 180 tons of dehydrated potatoes, 180 tons of sugar, 11 tons of coffee, 19 tons of powdered milk, 5 tons of whole milk for children, 3 tons of fresh yeast for baking, 144 tons of dehydrated vegetables, 38 tons of salt and 10 tons of cheese. In all, 1,534 tons were required each day to feed
13068-414: The response. Given all required funding and development support, the team produced working radar systems in 1935 and began deployment. By 1936, the first five Chain Home (CH) systems were operational and by 1940 stretched across the entire UK including Northern Ireland. Even by standards of the era, CH was crude; instead of broadcasting and receiving from an aimed antenna, CH broadcast a signal floodlighting
13200-529: The resulting "Green Garlic" did not meet all of the requirements for the original MEW, it was close enough and would be available years earlier. The decision was made to make the MEW a long-term development with additional features such as moving target indication while the Green Garlic would be mated to an enormous antenna that would give it range over 200 nautical miles (370 km; 230 mi). Installations, under
13332-460: The resulting frequency spectrum will contain harmonic frequencies above and below F T {\displaystyle F_{T}} with a distance of F R {\displaystyle F_{R}} . As a result, the Doppler measurement is only non-ambiguous if the Doppler frequency shift is less than half of F R {\displaystyle F_{R}} , called
13464-427: The roadside to detect stranded vehicles, obstructions and debris by inverting the automotive radar approach and ignoring moving objects. Smaller radar systems are used to detect human movement . Examples are breathing pattern detection for sleep monitoring and hand and finger gesture detection for computer interaction. Automatic door opening, light activation and intruder sensing are also common. A radar system has
13596-484: The same time, Soviet military aircraft began to violate West Berlin airspace and would harass, or what the military called "buzz", flights in and out of West Berlin. On 5 April, a Soviet Air Force Yakovlev Yak-3 fighter collided with a British European Airways Vickers Viking 1B airliner near RAF Gatow airfield , killing all aboard both aircraft. Later dubbed the Gatow air disaster , this event exacerbated tensions between
13728-407: The scattered energy back toward the source. The extent to which an object reflects or scatters radio waves is called its radar cross-section . The power P r returning to the receiving antenna is given by the equation: where In the common case where the transmitter and the receiver are at the same location, R t = R r and the term R t ² R r ² can be replaced by R , where R
13860-467: The signal is attenuated by the medium the beam crosses, and the beam disperses. The maximum range of conventional radar can be limited by a number of factors: Berlin Blockade American-allied victory The Berlin Blockade (24 June 1948 – 12 May 1949) was one of the first major international crises of the Cold War . During the multinational occupation of post–World War II Germany ,
13992-568: The sites would be upgraded with hardened bunkers to allow them to survive a near miss. The Berlin Blockade of July 1948 led to concerns about the next war's estimated time-frame. A White Paper on the state of the network was completed in March 1949. This found that the stations were in a terrible state, with many of them suffering weather damage and a number of them having been broken into and vandalized. A complete defense would also require 1152 fighters and 265 AA regiments, of which only 352 fighters and 75 regiments were actually available. All of this
14124-616: The states in the US zone to form a co-ordinating body, the so-called council of states ( Länderrat ), with the power to legislate for the entire US zone. It created its own central bodies called joint interstate committees ( Ausschüsse ) headed by a secretariat seated in Stuttgart . While the British and Soviet central administrations were allied institutions, these US zone committees were not OMGUS subdivisions, but instead were autonomous bodies of German self-rule under OMGUS supervision. Representatives of these three governments, along with
14256-527: The states, the central offices, political parties, trade unions, and consumer organisations. As indicated by its name, the zonal advisory board had no legislative power, but was merely advisory. The Control Commission for Germany – British Element made all decisions with its legislative power. In reaction to the Soviet and British advances, in October 1945 the Office of Military Government, United States (OMGUS) encouraged
14388-491: The target. If the wavelength is much shorter than the target's size, the wave will bounce off in a way similar to the way light is reflected by a mirror . If the wavelength is much longer than the size of the target, the target may not be visible because of poor reflection. Low-frequency radar technology is dependent on resonances for detection, but not identification, of targets. This is described by Rayleigh scattering , an effect that creates Earth's blue sky and red sunsets. When
14520-519: The technology with the U.S. during the 1940 Tizard Mission . In April 1940, Popular Science showed an example of a radar unit using the Watson-Watt patent in an article on air defence. Also, in late 1941 Popular Mechanics had an article in which a U.S. scientist speculated about the British early warning system on the English east coast and came close to what it was and how it worked. Watson-Watt
14652-487: The threat of the West's ability to retaliate with nuclear weapons if necessary, the Soviets possibly knew that none of the bombers were atomic-capable. The first Silverplate bombers only arrived in Europe near the end of the crisis in April 1949. General Lucius D. Clay , in charge of the US Occupation Zone in Germany, summed up the reasons for not retreating in a cable on 13 June 1948, to Washington, D.C.: There
14784-879: The transmitter. The reflected radar signals captured by the receiving antenna are usually very weak. They can be strengthened by electronic amplifiers . More sophisticated methods of signal processing are also used in order to recover useful radar signals. The weak absorption of radio waves by the medium through which they pass is what enables radar sets to detect objects at relatively long ranges—ranges at which other electromagnetic wavelengths, such as visible light , infrared light , and ultraviolet light , are too strongly attenuated. Weather phenomena, such as fog, clouds, rain, falling snow, and sleet, that block visible light are usually transparent to radio waves. Certain radio frequencies that are absorbed or scattered by water vapour, raindrops, or atmospheric gases (especially oxygen) are avoided when designing radars, except when their detection
14916-487: The two length scales are comparable, there may be resonances . Early radars used very long wavelengths that were larger than the targets and thus received a vague signal, whereas many modern systems use shorter wavelengths (a few centimetres or less) that can image objects as small as a loaf of bread. Short radio waves reflect from curves and corners in a way similar to glint from a rounded piece of glass. The most reflective targets for short wavelengths have 90° angles between
15048-467: The use of radar altimeters possible in certain cases. The radar signals that are reflected back towards the radar receiver are the desirable ones that make radar detection work. If the object is moving either toward or away from the transmitter, there will be a slight change in the frequency of the radio waves due to the Doppler effect . Radar receivers are usually, but not always, in the same location as
15180-399: The various additional routes that were later proposed. The Soviets also granted only three air corridors for access to Berlin from Hamburg , Bückeburg , and Frankfurt . In 1946 the Soviets stopped delivering agricultural goods from their zone in eastern Germany, and the American commander, Lucius D. Clay , responded by stopping shipments of dismantled industries from western Germany to
15312-401: The war, by excessive printing, resulting in many Germans using cigarettes as a de facto currency or for bartering. The Soviets opposed western plans for a reform. They interpreted the new currency as an unjustified, unilateral decision, and responded by cutting all land links between West Berlin and West Germany. The Soviets believed that the only currency that should be allowed to circulate
15444-652: The wishes of the Soviet government by "regulating" access to Berlin. The Allied Control Council (ACC) met for the last time on 20 March 1948, when Vasily Sokolovsky demanded to know the outcome of the London Conference and, on being told by negotiators that they had not yet heard the final results from their governments, he said, "I see no sense in continuing this meeting, and I declare it adjourned." The entire Soviet delegation rose and walked out. Truman later noted, for most of Germany, this act merely formalised what had been an obvious fact for some time, namely, that
15576-608: Was a 1938 Bell Lab unit on some United Air Lines aircraft. Aircraft can land in fog at airports equipped with radar-assisted ground-controlled approach systems in which the plane's position is observed on precision approach radar screens by operators who thereby give radio landing instructions to the pilot, maintaining the aircraft on a defined approach path to the runway. Military fighter aircraft are usually fitted with air-to-air targeting radars, to detect and target enemy aircraft. In addition, larger specialized military aircraft carry powerful airborne radars to observe air traffic over
15708-470: Was also divided into four occupation zones, despite the city's location, 100 miles (160 km) inside Soviet-controlled eastern Germany. The United States, United Kingdom, and France controlled western portions of the city, while Soviet troops controlled the eastern sector. In the eastern zone, the Soviet authorities forcibly unified the Communist Party of Germany and Social Democratic Party (SPD) in
15840-417: Was coal, on 278,228 flights to Berlin. In addition Canadian , Australian , New Zealand and South African air crews assisted the RAF during the blockade. The French also conducted flights, but only to provide supplies for their military garrison. American C-47 and C-54 transport airplanes, together, flew over 92,000,000 miles (148,000,000 km) in the process, almost the distance from Earth to
15972-589: Was completed in 1957 after the introduction of the Type 80 radar and after many ROTOR stations had already closed. The site was within Exmoor National Park and its creation was strenuously opposed by the National Trust who lost no time in obliterating the site immediately after closure. Many of the buildings have been re-purposed since being active as ROTOR sites. An example is the Bawburgh R4 SOC which
16104-507: Was deterrence, and if that failed, interceptor aircraft and missiles would have no measurable effect on the eventual outcome. ROTOR was initially to be replaced by a new network dedicated largely to defending the V-bomber force, the "1958 Plan". This role was eventually abandoned, leaving only the task of locating aircraft carrying jammers to keep the BMEWS radars free from interference and prevent
16236-542: Was given extreme urgency with the 29 August 1949 test of the first Soviet atomic bomb . That month, a new directive stated RAF Fighter Command 's mission was the defense of Great Britain. It was known that the Soviets had made exact copies of the B-29 Superfortress as the Tupolev Tu-4 , and these aircraft had the performance needed to reach the UK with a nuclear payload. These were fast, but not fast enough to escape
16368-618: Was mainly carried out by the Marconi Wireless and Telegraph Company in several phases, called ROTOR 1, ROTOR 2 and ROTOR 3. As work on the Microwave Early Warning system began, researchers at the Royal Radar Establishment were experimenting with new cavity magnetrons and crystal detectors that, combined with a ad hoc antenna, increased the range of their existing microwave radars on the order of four times. While
16500-490: Was now known as the Microwave Early Warning , which was expected in the 1957 time-frame. Interception guidance would still be handled by existing systems in either case. All of the radars were to be improved in terms of siting, with the addition of hardened control bunkers to protect the operators from a conventional attack. On the east coast, where a Soviet attack would be most likely, the bunkers were underground in
16632-402: Was re-purposed as SRHQ4.1 and then RGHQ4.1 to suit the evolving needs of government. The building is intact, but it has been significantly reconfigured since its use as a ROTOR SOC, notably with the addition of an extra floor and the flooring-over of the original R4 operations well. July 2019; Kent Underground Exploration are starting talks with TDC hoping to be given access to find and uncover
16764-426: Was reduced by 50% to about 15 billion marks and stretched out over 30 years, and compared to the fast-growing German economy were of minor impact. In response to the announcement of the first of these meetings, in late January 1948, the Soviets began stopping British and American trains to Berlin to check passenger identities. As outlined in an announcement on 7 March 1948, all of the governments present approved
16896-512: Was sent to a network of control stations, mostly built underground, using an extensive telephone and telex network. Work also began on a new microwave frequency radar to replace Chain Home c. 1957 . The experimental system Green Garlic was so successful that it began replacing Chain Home starting in 1954. In service, these proved so accurate that they could replace the Type 7 radars as well, and their greatly improved range meant that fewer radars would be needed to provide coverage over
17028-748: Was sent to the U.S. in 1941 to advise on air defense after Japan's attack on Pearl Harbor . Alfred Lee Loomis organized the secret MIT Radiation Laboratory at Massachusetts Institute of Technology , Cambridge, Massachusetts which developed microwave radar technology in the years 1941–45. Later, in 1943, Page greatly improved radar with the monopulse technique that was used for many years in most radar applications. The war precipitated research to find better resolution, more portability, and more features for radar, including small, lightweight sets to equip night fighters ( aircraft interception radar ) and maritime patrol aircraft ( air-to-surface-vessel radar ), and complementary navigation systems like Oboe used by
17160-443: Was the currency that they issued themselves. Anticipating the introduction of a new currency by the other countries in the non-Soviet zones, the Soviet Union in May 1948 directed its military to introduce its own new currency and to permit only the Soviet currency to be used in their sector of Berlin if the other countries brought in a different currency there. On 18 June the United States, Britain and France announced that on 21 June
17292-411: Was the first to use radio waves to detect "the presence of distant metallic objects". In 1904, he demonstrated the feasibility of detecting a ship in dense fog, but not its distance from the transmitter. He obtained a patent for his detection device in April 1904 and later a patent for a related amendment for estimating the distance to the ship. He also obtained a British patent on 23 September 1904 for
17424-523: Was the work of the later concurrent Operation Little Vittles in which candy-dropping aircraft dubbed " raisin bombers " generated much goodwill among German children. Having initially concluded there was no way the airlift could work, the Soviets found its continued success an increasing embarrassment. On 12 May 1949, the USSR lifted the blockade of West Berlin, due to economic issues in East Berlin, although for
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