ASV Mark II radar - Knowledge (XXG)

967: 976: 40: 606:. Radio signals hitting the target directly were returned to the receiver, but so was any signal reflecting forward off the water close to the ship, as this signal would also strike the ship and reflect back to the receiver. Whereas aircraft were difficult to detect beyond about 4 miles (6.4 km), ships could be easily detected at distances on the order of 10 miles (16 km). Any vertical surface worked in this way, including seaside cliffs, which could be picked up at very long range and proved to be extremely useful for navigation. 703: 297: 888: 1366: 1274: 599:

in front of the aircraft and scattering off waves would cause a ground return. Even then the signal was relatively small compared to the huge ground return seen in the AI case, and only caused problems within about 0.5 miles (0.80 km) of the aircraft, although this could grow to as much as 4.5 miles (7.2 km) in high sea states. This would turn out to be an important limitation in practice, but one that was ultimately solved in a roundabout fashion.

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useless for attacks, as they could not reliably detect submarines, the only German ships in the area. Testing had shown the maximum detection range on a surfaced submarine was about 5.5 miles (8.9 km), so in a high sea state with the minimum range of 4.5 miles, this left little room for detection. But they did find the sets useful for stationkeeping over the convoys, as well as navigating by looking at the returns from sea cliffs.

807: 1166:, which was originally intended to be used in a similar role for night fighters. This was not nearly as powerful as Leigh's version, but was smaller and already available in some numbers. In spite of great effort, the Turbinlite never worked satisfactorily. It was not until late in 1941 before the Ministry admitted this and returned to de Leigh's original design. He had continued to develop it in secret during this time. 1143:

1,000 yards was too long a range for the submarine to be spotted visually at night except under perfect conditions, like a full moon. The same problem affected the AI radars as well, but in that case was far more serious due to the small size of the aircraft targets compared to a U-boat or ship, and the team had invested considerable effort in trying to solve this "minimum range controversy", so far unsuccessfully.

1177:. From that point on, the combination of ASV Mk. II and Leigh light proved extremely effective. So many submarines were being attacked by the end of the summer that leaving base at night, formerly entirely safe, was now considered suicidal. The Germans were forced to leave their bases during the day so they could at least see the attacking aircraft and put up a fight, but this proved little safer. 1192: 1407: 1124: 468: 1018:

approaches to a convoy by flying 10 miles to one side of it, sweeping a 20-mile wide path. Submarines were not fast enough to cross that distance before the aircraft had returned for another sweep. There was some discussion of giving it a special display to make interpretation easier, but it went into service using the original ASV display instead.

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forward rather than down, in keeping with an aircraft flying at 2,000 feet (610 m) rather than 20,000 feet (6.1 km) altitude. He continued working on this project with the primary developers of H2S, EMI. In late 1942, the ASVS version of Mark III was cancelled and the H2S-based version was ordered into production.

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was that these aircraft tended to fly at slower speeds, which meant that larger antennas could be used for better reception without seriously affecting aircraft performance. The early units used standard quarter-wave dipoles mounted on the nose area, but these were later extended to three-quarter wave in production units.

651:'s experimental 45 MHz television service and had built receivers that they still might have on-hand. Bowen visited the company in April or May, and found that they had "scores and scores" of the receivers in a production-ready form. When they tested them, they were found to be far superior to the EMI models. 615: 1589:

It is stated that the operator would look for changes in the pulse repetition frequency, but existing references suggest ASV did not have this feature. It is more likely this refers to the change when the aircraft switched from the broadside array to the forward-looking antennas, as this would double

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There was considerable desire to allow the system to have a second display in front of the pilot, so they could navigate directly without verbal instructions from the radar operator. However, in spite of considerable effort from 1940 through 1943, they were unable to make a version that could be seen

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While Mk. II was in the midst of achieving some of its greatest successes, in the late summer of 1942 crews returned to base claiming that good detections on German U-boats were followed by the ships disappearing as they moved in for the approach. It was quickly surmised that the Germans were fitting

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in Wales was selected and the team moved into a hangar on the airfield in November 1939. Conditions turned out to be little better than Perth, and the team was forced to work in freezing temperatures as the hangar doors had to be left open. Nevertheless, by the end of December they had managed to fit

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The Mk. I and Mk. II units were generally similar electronically but differed in their operating frequency and packaging. The main difference was that the Mk. I receiver and display were packaged in a single large box, which meant the entire unit had to be replaced if there was a problem with either

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Studying the statistics of attacks during 1942 in the Bay of Biscay, the RAF was able to determine that the system had first been introduced in June and had become largely universal by September. By comparing the distance at which the submarine was detected and then when it was lost, they calculated

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As a result, Mk. II was far more reliable than Mk. I; it did not offer increased performance, but maintained that performance in spite of rough service and was much easier to fix in the field. The only other major change was to move the operational frequency from 214 MHz to 176 MHz because

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transponder at the base, tuned to operate on the ASV frequencies. The IFF system broadcast a short pulse of radio signal whenever it heard the pulse from one of the ASV radars, and its signal was so powerful that the crews could pick it up at 50 to 60 miles (80–97 km) from base, making the

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employee had been told to begin building the receivers and asked for an example, but the team had only one airworthy receiver and had to give them an old hand-assembled bench model with the instructions that it wasn't to be used for a production design. Sure enough, Metrovick returned a design based

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In comparison, when the same signal hit the water it tended to reflect rather than scatter, sending the majority of the signal forward and away from the aircraft. The only time the signal could be seen is when the aircraft approached the water very closely when some of it would strike the water just

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ASV proved easy to develop for a variety of reasons. One was that the host aircraft tended to be very large, so equipment size and weight were not as critical as it was in the much smaller night fighters. It was also easier to move around in these aircraft while fitting the equipment. Another reason

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being a common solution. CH worked at wavelengths on the order of 10 metres, which called for antennas about 5 metres (16 ft) long, far too large to be practically carried on an aircraft. Through 1936 the team's primary concern was the development of radio systems operating at much shorter

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The "long range" antennas were in two sets. The transmitter was a single Yagi extending from the nose, and two receiver Yagis, typically under the wings, angled outboard at about 15 degrees. The broadside array was normally arranged with a Sterba curtain running back along the top of the aircraft's

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The first tests of Vixen were carried out in June 1943 and were generally successful, with some issues. The main one was that the muting was created by a shorted antenna, and as it was adjusted it caused the loading on the transmitter to change, which led to changes in the output signal. These were

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Another solution to the Metox problem was implemented in the "Vixen" system. This allowed the strength of the signal from the ASV's transmitter to be muted down. By timing this process carefully, the radar operator could fool the radio operator on the submarine into thinking the aircraft was flying

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The Tizard mission was in Ottawa for only two days before leaving for Washington. During that time the NRC radio teams pored over the ASV unit, trying to learn everything they could of its design before it left for the US. This led to a debate on whether to continue development of their own system,

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In early 1940 there was a lengthy debate within the Air Ministry, and the government in general, about whether or not the United States should be told of the many technological developments taking place in the UK. The UK was suffering from a lack of manpower and production capacity, problems the US

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into a streamlined container with a lens that spread the beam so it covered an area several degrees wide at a range of 1,000 yards (910 m), about the same angle as the beam of the radar. It would be turned on just as the signal disappeared on the radar screen, lighting the target and allowing

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In spite of the system's ability to detect submarines at night, attacking them was not a simple matter. After finding the rough location on the broadside array, the target was plotted on a map and the aircraft maneuvered so it could begin to approach it using the forward-facing antennas. These had

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personally overrode any remaining objections, and tasked Henry Tizard with making the arrangements. After considering the many technologies being developed, Tizard's team ultimately chose four to take with them; AI Mk. IV, ASV Mk. II, IFF Mark II, and the new cavity magnetron that made radars much

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The combat history of the Mk. II was extensively studied and detailed statistics were collected on its performance. In operational conditions against surfaced submarines, the original SRASV antennas averaged 5.6 miles (9.0 km) range when flying at 2000 feet. The LRASV's forward antennas

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The Mk. II operated on a frequency of 176 MHz ±5 MHz. It sent out pulses about 2.5 μS long 400 times a second. The peak power was about 7 kW. The signals were sent through a rotating switch that alternated with each pulse, sending and receiving the signal on either side of the

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and U-boat losses began to climb again due to intercepts revealing their positions and orders. This was combined with a key piece of false information planted by a captured British officer, who claimed their aircraft were equipped with a device to listen for the very weak signals given off by the

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The effects were summarized in an early-1943 study. They showed that before the introduction of Metox, an aircraft without radar would spend 135 hours in the air for every U-boat it detected, while one equipped with ASV saw one for every 95 hours of flight. From October, when Metox was common, it

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This event broke the ice, and soon the two teams were planning a complete development and production schedule for all of the British designs. It was eventually agreed that US companies would begin producing the ASV and AI 1.5 m sets while beginning research on new radars using the magnetron.

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After significant confusion and argument between Coastal and Bomber Command, the ASV Mk. III began to arrive in the spring of 1943, and after some rather disappointing sorties in March, the Wellingtons began making successful attacks late that month. This was the same period in which several new

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after the Paris-based company that produced them, was a simple system. When a pulse on the correct frequency was received, it sent out a short pulse of audio in the radio operator's headphones. The operator could listen for the strength and pattern of the signals to determine if the aircraft was

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The new ASV Mk. II design was essentially a rationalized and cleaned up Mk. I, differing little in terms of the electronics, but considerably in terms of layout, wiring and construction. Among the changes was the separation of the receiver electronics from the display so either could be fixed by

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aircraft. The reports noted that the system was useful for detecting ships at night or in bad weather, but suffered from the fact that enemy shipping typically hugged the coastline where the returns from the land often swamped the ship's returns. It was also useful for guiding an attack when the

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Test flights began in late 1939, and they were used operationally in the first months of 1940. It would be some time before the related AI Mark IV sets became operational in July 1940, making ASV the world's first operational airborne radar system. At first the crews found the system relatively

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Throughout this period, Hanbury Brown was convinced the H2S could also be used for anti-shipping work, with suitable modifications. The primary issues were reducing the size of the antenna to fit in Coastal Command's smaller aircraft, and modifications to the antenna to send the signal further

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The broadside array offered about 2.5 times the gain of the original system. This allowed it to detect moderate-sized ships at 40 miles (64 km) and surfaced submarines at 10 to 15 miles (16–24 km), an enormous advance over the Mk. I style antennas. The aircraft could scan the

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was sent to the Netherlands to pick up the Philips board of directors, while two cargo ships were sent to pick up 25,000 EF50s, and 25,000 more bases which Mullard could build additional tubes while a new production line was set up. The ships left as the German attack on the Netherlands was

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AI and ASV developed in parallel for some time. In May 1938 the team received the Western Electric 4304 tubes which replaced the 316As doorknobs in the transmitter and improved transmit power to 2,000 W. In testing this proved to increase detection range on ships to 12 to 15 miles

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was still much more powerful than the reflection from a target. An aircraft flying at the typical German bomber altitude of 15,000 feet (4.6 km) could only see aircraft within 15,000 feet, anything beyond that was hidden in the ground return. This was a much shorter range than the

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For the next year, Bowen's team found themselves working much more on the ASV than AI. Much of this involved the development of new antenna systems, more advanced than the system on the Anson where a dipole was held outside the escape hatch and rotated by hand to hunt for signals. Among the

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The system was installed on six Sunderlands, under the name Mark IIA, in the spring of 1943. While the system did demonstrate much greater range, it was found that the sea return off waves was also much more powerful. By this point Metox was universal, and the extra signal gave the U-boats

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Two receivers were used, the first was the R.3039 using VR95 acorn valves, and the later R.3084 using VR136 pentodes and VR137 triodes. Both Pye and EKCO built both versions, and there were a number of minor differences. EKCO's included an output for a recorder and several other changes.

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But the real problem was that the minimum range of the radar was about 1000 yards at best; at shorter distances the returns from the target merged with the leftover signal from the transmitter and became invisible in the electronic noise and scattering off the water. Unfortunately,

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ultimately not considered important, and it was suggested it be fit on all ASV aircraft. However, production was not ordered until November 1943 and the first sets did not arrive until February 1944, by which point ASV Mk. III had largely taken over. Vixen was not used operationally.

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This Coastal Command Liberator mounts both sets of LRASV antennas. On the nose and under the wings are the Yagi arrays for forward-search, and the port broadside array can be seen just about the roundel on the side of the fuselage. The aircraft two away is equipped with ASV Mk.

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By the early part of 1940, Hudsons were arriving at the rate of two or three a week, and the crews were able to quickly fit the sets due to the easy working environment in the large fuselage. At this time, the team was large enough that they were able to send a small group to

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aircraft within 30 days. When the units started arriving, they found the Metrovick transmitter was also the bench model, and when they protested, Metrovick noted that Watt had personally visited the factory and told them to put it into production because it was known to work.

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which also made use of the Pye strip. The first Mk. II units began to arrive in the summer of 1940, and by October 1940, 140 transmitters, 45 receivers and 80 displays had been delivered. By the end of March 1941 that had increased to 2,000 transmitters and 1,000 receivers.

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The first ASV using production parts was hand-fitted to a Walrus and sent to Gosport for testing. This version ran at a nominal 1.5 m wavelength, at 214 MHz. Flying at only 20 feet (6.1 m) over the water, the radar easily detected ships all around the Solent.

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Another attempt to improve the performance of the system was the introduction of a new transmitter, T.3140. This produced over ten times the signal, averaging 100 kW per pulse, and thereby increased the overall range and performance. This required a more powerful

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The complete system consisted of several separate boxes that could be easily removed for servicing. The main boxes where the Type 3040 (T.3040) transmitter, built by EKCO, the receiver, built by Pye or EKCO, and the Type 6 or Type 96 "indicator units", the CRTs.

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This display simulates a typical scene on the ASV Mk. II. At the bottom is a large triangular blip caused by the transmitter signal and the local ground return. Above that is a smaller blip indicating a target at about nine miles range and to the right of the

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As supplies of the Mk. III improved, Mk. II-equipped aircraft were sent to secondary theaters where they served out the war. Examples with the original dipole antennas were in service as late as 1943, by which time they were known as SRASV, for "Short Range".

326:. Tizard was aware that a fighter pilot might be expected to see a bomber at about 1,000 yards (910 m) at most, whereas the accuracy of the CH system was perhaps 5 miles (8.0 km). He wrote a memo on the topic on 27 April 1936 and sent it to 1217:

that as many as 50% of the U-boats were diving before the ASV even saw them. What was once dismissed as a minor issue was now clearly a significant problem. For the first time since the introduction of ASV, shipping losses once again began to rise.

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sinking the next day. By mid-1941 the ASV radar had increased daytime attacks on U-boats by 20%, and made night attacks possible for the first time. The first successful night attack on a U-boat was carried out by a Swordfish on 21 December 1941.

745:(some distance from Dundee) that was utterly unsuitable for fitting. Nevertheless, radar sets and aircraft started to arrive, along with new demands from the Fleet Air Arm to equip some of their aircraft with ASV in Swordfish and Walrus aircraft. 1373:

The original "short range" antennas consisted of receiver unipoles extending horizontally out from either side of the nose of the aircraft. Behind them were the transmitters, which was a similar unipole but also included a reflector behind it.

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On its first flight the set demonstrated very limited range against aircraft. However, while flying the aircraft about, the operators saw odd returns appearing on the display. They finally realized these were from the wharves and cranes at the

662:"Miniwatt", which had been designed specifically for efficient VHF use. The tubes were labeled Mullard, Philip's UK subsidiary. When they investigated, Mullard told the Air Ministry that the tubes were actually built at Philips' factory in 1041:. However, the radar concepts were believed to be among some of the most advanced in the world, and giving them to the US would mean surrendering some of the UK's best ideas to exploitation by what was then still a non-aligned party. 1327:

anti-submarine technologies were arriving, and from April through July these combined to result in a huge number of losses to the U-boat fleet. By the end of June, cargo shipping losses to U-boat attacks had dropped almost to zero.

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Experiments demonstrated that the main problem causing short range was the low gain of the antennas. Given the low speeds of the aircraft, so that drag was not a significant issue compared to the AI role, the team was able to use

349:. If the airborne radar had a range of about 5 miles, CH could be tasked with getting the fighter into the general area, and then the fighter's own radar could take over and guide them until the enemy could be seen visually. 737:

in Scotland, only to find that nothing had been prepared. The rector had only vague memories of a conversation on the topic with Watt, and by now the students had returned for the fall term and there was little available room.

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and provided complete details of the required design, but when they returned their first attempt six months later it was completely unusable. When they asked for improvements, Cossor never responded, too busy with other work.

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improved to this 6.3 miles (10.1 km) while the broadside array further increased this to 6.9 miles (11.1 km). It was found that flying at lower altitudes reduced the detection range, but also the amount of clutter.

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An order for 4,000 units was placed with EKCO and Pye. For reasons unknown, the contract negotiations required considerable time to finalize, and throughout the production run it battled for precedence with the AI units and

1319:(Metrovick) to develop the lash-up ASVS into a useful airborne system as ASV Mark III. They had a suitable system ready by the summer of 1942, although the first deliveries would not be available before the spring of 1943. 251:

was introduced, allowing the U-boat to be picked up visually after it passed off the radar display. With the introduction of the Leigh light, nighttime U-boat interceptions became common, and turned the German ports in the

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complained that it would be much better if radars worked at microwave frequencies and explained their frustration that existing microwave devices had power of only a few watts. Bowen reached into his lock box and produced

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By this time, Watt had moved to Air Ministry headquarters in London. He heard of the successful test and called the team to ask if they would be available for a demonstration in early September. Plans were underway to run

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away from them. This had little effect on the performance of the radar as it approached the target, as even with less signal being broadcast the reduction in range more than made up for any loss of power from the muting.

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By the end of July 1939, the team finally had everything in place and an order for twenty-four units was sent out. Metrovick would build the transmitters, Pye was already ramping up production of what became known as the

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pulling the beam vertically from the bottom to the top of the screen. Received signals would deflect the beam to the left or right depending which antenna was active at that time. The operator compared the length of the

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experiments was a motorized rotating dipole that scanned the entire area around the aircraft and displayed angles as the X-axis and range on the Y-axis. This appears to be the first example of what is today known as a

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The Metox detector was a simple affair, consisting of a cross-shaped antenna that was swung by hand, and a radio receiver inside the submarine. Coastal Command pilots who saw the new antenna nicknamed it the "Biscay

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the number of pulses painting the submarine as long as it was roughly in front of the aircraft and visible to both antennas. This would indicate the aircraft is now approaching rather than simply scanning the area.

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launching aircraft in a futile effort to intercept them. The weather was so bad that the operators had to use the radar as a navigation system to find their way home, using the reflection off seaside cliffs.

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The Mission's arrival in Washington initially led to similar surprises when the team learned that the US Army and Navy had developed radars similar to the British Chain Home and Chain Home Low. However, the

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asked to take on the project, and formed a small team to consider the problem in August 1936. They gave the concept the name RDF2, as Chain Home was at that time known as RDF1. This would later be known as

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In June 1941 a formal application to the Director of Communications Development (DCD, at that time run by Robert Watt) to form a separate group to develop ASVS was approved, but development was slow.

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in all directions, sending some part of the signal back towards the aircraft. Although only a small portion of the original signal was returned, the ground was essentially infinite in size so this

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using two of these tubes working at 1.25 m wavelength; below 1.25 m the sensitivity dropped off sharply. Gerald Touch converted the EMI receiver to the same frequency by using it as the

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took ASV aircraft 135 hours, meaning Metox had seemingly rendered ASV useless. However, the time taken to find a U-boat without radar had also increased, to 245 hours, so ASV was still useful.

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Later, a switching unit was introduced, the Aerial Coupling Box Type 8, which allowed a single antenna to be switched from transmitter to receiver. This was used on smaller aircraft like the

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in the US. This set worked on the relatively short wavelength of 67 cm, about half that of the British 1.5 m set. A prototype was working by November and was making some progress.

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Metox's intermediate frequency stage. This led to early 1943 orders from German Naval High Command to turn off the Metox, which allowed Mk. II to once again become effective for a time.

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U-71 was launched on 31 October 1940 and spent some time in the Kiel area. This leaves little time for it to move to Biscay before it was attacked. Further verification would be useful.

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using the new VT90 tubes (later known as CV62) in the transmitter, while the AI Mk. II would use the older DET12 and TY120s. This meant the ASV would be somewhat more advanced than AI.

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to their boats and diving when they saw an aircraft approaching. This possibility had been considered in October 1941, but at the time there seemed to be no reason to stop using ASV.

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teams who had developed both AI and ASV, and had now turned their attention to AIS and ASVS, the S standing for "senitmetric". Tests in April 1941 with early lash-up devices against

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Type 316A doorknob vacuum tubes. These were suitable for building transmitter units of about 20 W continual power for wavelengths of 1 to 10 m. Percy Hibberd built a new

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At a meeting in London on 30 November 1939, the relative priorities for Chain Home, Chain Home Low, AI and ASV were discussed. Bowen finalized plans to build the ASV radios at

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by the pilot during the day while also not blinding them at night. Eventually, they gave up on the idea in favour of training the operators to give standardized instructions.

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In February 1940 a collection of early combat reports was compiled in order to better understand how to improve the system. By this time the Mk. I had also been installed on

666:, and that attempts to start production in the UK had failed due to problems manufacturing the bases. The bases used a new design that was key to the way the tubes operated. 602:

Finally, the shape of the targets as seen from the radar were ideal for detection. The side of the ship, rising vertically from the surface of the water, created a partial

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While waiting for the Metrovick and Cossor receivers to arrive, there was a chance encounter between Bowen and his former professor at King's College, Nobel prize winner

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at a distance of 5 to 6 miles (8.0–9.7 km). As they approached the ships the Anson eventually became visible through the clouds, and the team could see the

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part. The signals were also slightly different, with the Mk. I producing the same 7 kW power, but with a pulse width of 1.5 μS and a PRF of 1200 Hz.

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less gain and picked up the submarine at shorter ranges, so there was a possibility the submarine could escape as they switched from side to forward approach.

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number 6. This device produced pulses of about 10 kW, hundreds of times more than US devices, and newer models were soon producing ten times that amount.

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would build the British ASV unit as-is, building a new factory for its construction. Several thousand units were ultimately produced, mostly sold to the US.

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at a range of 2 to 3 miles (3.2–4.8 km). This was particularly impressive given the very low power of the transmitter, about 100 W per pulse.

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Watt met with his researchers at the local Crown and Castle pub, and agreed that the best solution was to introduce a small radar that could be mounted in a

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tuned to its frequencies. This was soon followed by British pilots reporting submarines diving as the aircraft began to approach. A new design based on H2S,

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had arrived at Perth, and through contacts in the Air Ministry, managed to convince them that the site was unsuitable for their work. A new location at

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with much higher gain. Typical installations had the transmitter on the front of the nose, and two receivers under the wings, pointed outward at their

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in December 1940, where it demonstrated its ability to detect large ships at a range of 60 miles (97 km). Production was immediately taken up by

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Smith, R.A.; Hanbury-Brown, Robert; Mould, A.J.; Ward, A.G.; Walker, B.A. (October 1985). "ASV: the detection of surface vessels by airborne radar".

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After the invention of the cavity magnetron in early 1940, all of the British forces began development of radars using the system, which generated

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in heavy overcast skies, torpedoing her and leading to her destruction the next day. Mk. II was only partially effective against the much smaller

51:(PBY Catalina). The transmitter is on top of the cockpit, the darker-colored port-side receiver is mounted below and to the right, angled outward. 814:

mounts the original short-range antennas, now painted bright yellow. By the time this aircraft left service they were used only as receivers for

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The first examples of the Leigh light started appearing in the early summer of 1942. The first success was on 5 July 1942 when a Wellington of

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miles south of Bawdsey. Shipping also appeared, but the team was unable to test this very well as the Heyford was forbidden to fly over water.

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This Hudson is equipped forward-firing LRASV antennas, with the transmitter on the nose and the receivers under each wing, angled outboard.

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bomber, which was no longer competitive and was being passed off to other uses. Brown took the chance to develop a new antenna, a type of

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noted that the first flight in a Wellington did not take place until December, and it was not until January 1942 that he noted "ASV saw

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on either side to determine which looked larger, and then used the intercom system to tell the pilot to correct in the right direction.

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A brief reprieve in the effects of Metox was at hand in December 1942, when British codebreakers once again were able to break into the

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whose shorter wavelength would make it more suitable for aircraft use, or to simply build the British unit using Canadian and US tubes.

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entered service in early 1940 and was quickly replaced by the greatly improved Mk. II. A single Mk. II was shipped to the US during the

2606: 782:. The Navy soon picked up development as the Type 286, and 200 such units would eventually be fitted to destroyers and torpedo boats. 39: 2738: 2717: 2675: 2654: 2627: 2585: 2564: 2363: 815: 730: 247:, especially as the signal faded as the aircraft approached the target and they would lose contact at night. To close the gap, the 721:

In early August, the team was informed that the Air Ministry had ordered 30 AI units and expected Bowen to have them installed in

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Early units worked on such long wavelengths that the only available aircraft that was large enough to carry the antennas was this

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While the transmitter problem was considered solved with the new tubes, the team had significant problems with the receivers. A

1038: 283:, was rushed to service, replacing the Mk. II beginning in 1943. Mk. II remained in use throughout the war in other theatres. 618:

The EF50 made airborne radars practical due to their relatively small size, good frequency response, and good power handling.

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wavelengths, eventually settling on a set working at 6.7 m, based on an experimental television receiver built at

1131: 1007: 586:(VHF) radio waves when interacting with water. In the case of AI, when the radar's signal hit the ground it tended to 355: 211: 187:. It was the first aircraft-mounted radar of any sort to be used operationally. It was widely used by aircraft of the 176: 717:. This particular aircraft also carried an experimental high-gain antenna under the wings, which cannot be seen here. 2052: 944: 415: 238: 107: 1552: 1357:

aircraft. The signals returned through the Pye strip amplifier, and every other pulse was electrically inverted.

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smaller and more powerful. They were also aware of and allowed to speak about other technologies, including the

702: 2782: 707: 296: 206:

The system was developed between late 1937 and early 1939, following the accidental detection of ships in the

911:

swapping them out separately, and using a selection of standard electrical connectors on all of the cables.

767:

and neatly solved the electrical problems they had been having. It was soon in use throughout the industry.

979:

On the Wellington, the broadside array shared a common transmit array spread along the top of the fuselage.

1174: 1147: 640: 399: 1246:

significant additional warning time. The system was ultimately built to the extent of only twelve units.

1551:

Some of these units were re-directed to the Navy as the Type 286 and to the Army as the basis for their

887: 840: 395: 1134:. The light could be aimed to point at the target without having to point the aircraft directly at it. 879:

cloud cover was below 1,500 feet (460 m), as they could press an attack without ever being seen.

195:

and similar groups in the United States and Canada. A version was also developed for small ships, the

1316: 1209: 1186: 1170: 984: 844: 832: 734: 562:

commented that "This, had they known, was the writing on the wall for the German Submarine Service."

555: 529: 437: 407: 301: 276: 1365: 1420: 1273: 1128: 1064:

For various reasons, the mission team first travelled to Canada where they met with members of the

991:

showed that it was possible to pick up surfaced submarines at limited range and in low sea states.

583: 522: 507: 350: 188: 904: 798:. January improved this to 18 AI and 12 ASV, numbers that continued to increase through the year. 654:

Much of the improvement in the Pye receiver was due to the use of a new type of tube developed by

1159: 370: 335: 272: 48: 2646: 907:

began designing a new set while working at the RAE. Hanbury Brown joined him in February 1940.

686: 2734: 2713: 2671: 2650: 2623: 2602: 2581: 2560: 2359: 1294: 1268: 1045: 1006:

Shortly after moving to St. Athan in 1939, Hanbury Brown received a request to fit ASV to the

673: 499: 280: 2694: 1395: 1094: 1034: 1000: 940: 892: 875: 836: 811: 722: 691: 603: 559: 391: 264: 234: 2033: 1073: 871: 795: 776: 742: 515: 456: 441: 425: 403: 366: 207: 2639: 2577:

Boffin: A Personal Story of the Early Days of Radar, Radio Astronomy and Quantum Optics

1202: 1058: 1027: 1011: 924: 786: 714: 374: 219: 1406: 858:

But the device became extremely useful after Squadron Leader Sidney Lugg installed an

806: 2776: 936: 828: 764: 710: 582:

But the major reason that ASV was easier to develop than AI was the behaviour of the

346: 339: 323: 316:

became concerned that the CH system would be so effective that the German air force (

253: 192: 983:

ASV had not been designed to detect submarines, but late 1939 testing by Hudsons of

895:. A system like this one was responsible for detecting, and ultimately sinking, the 706:

The Mk. I units used an antenna arrangement similar to the Mk. II unit seen on this

1290: 1225: 1054: 996: 916: 864: 790: 775:

was watching this performance and immediately ordered one fitted to his destroyer,

729:

To further confuse matters, when the war began on 1 September, the majority of the

510:

aircraft, and Watt wanted to crash the party. On the afternoon of 3 September 1937

327: 313: 184: 180: 931:

Mk. II scored its first success on 30 November 1940 when a Whitley Mk. VI damaged

2728: 2707: 2665: 2617: 2596: 2575: 2554: 2353: 839:. The group was able to quickly fit ASV Mk. I to these aircraft, followed by the 1151: 1118: 859: 373:

has to be on the same order of length as the wavelength of the signal, with the

248: 2053:"With Gallantry and Determination; The Story of the Torpedoing of the Bismarck" 669:

This led to a hurried effort to start production at the Mullard factories. The

467: 263:-frequency ASV radar, ASVS, was under development since 1941, but the required 2641:

Radar Development in Canada: The Radio Branch of the National Research Council

1304: 1286: 1239: 1191: 1163: 1050: 848: 587: 538:

The next day they took off at dawn and, in almost complete overcast, detected

503: 471: 422: 362: 309: 196: 2698: 1449:

According to Bowen, production of the Mk. I and II amounted to 24,600 units:

2760: 2754: 794:

17 AI radars in Blenheims, and 3 ASVs in the newly arriving Coastal Command

756: 755:

Another chance encounter after the meeting led Bowen to try a new material,

670: 663: 627: 444:

interfering with the receiver, but this was soon resolved by fitters at the

318: 268: 260: 117: 949:

as it attempted to return to France for repairs. This detection led to the

1300:

showed they could detect semi-submerged submarine at several miles range.

1242:

and the transmitter assembly was twice the weight of the original T.3040.

903:

Based on the experiences of the Mk. I units in the field, in January 1940

440:

to test this role. Early tests demonstrated a problem with noise from the

17: 2056: 1312: 644: 421:

With this accidental discovery of ship detection, the team was given two

1277:

One of the first fits of ASV Mk. III was on this Vickers Wellington XII

1127:

A crewman cleans the Leigh Light mounted under the starboard wing of an

1123: 623:(19–24 km), although in the AI role the range was little improved. 2355:

Delusions of Intelligence: Enigma, Ultra, and the End of Secure Ciphers

1416: 1378:

fuselage, with sets of dipoles running down the sides of the fuselage.

1106: 1089: 988: 655: 572: 455:

with Touch and Keith Wood aboard immediately detected shipping in the

1069: 632: 244: 223: 680:

proceeding and the docks were under constant threat of air attack.

1405: 1364: 1272: 1190: 1122: 974: 965: 886: 867:

much less eventful. The crews took to naming the beacon "Mother".

805: 701: 613: 466: 295: 2004: 2002: 361:

The major problem faced by the Airborne Group was the problem of

749: 659: 308:

Early during the development of the first British radar system,

45: 2034:"Electronic Equipment, ASV (Air-To-Surface Vessel Radar) Mk II" 614: 2730:

Top secret exchange: the Tizard mission and the scientific war

2105: 2103: 2101: 690:

receiver, and Pye had also begun experimental production of a

648: 379: 230:

in Canada, with over 17,000 produced for use in the US alone.

1155:

the last seconds of the approach to be carried out visually.

631:

on this model, which proved useless. The team also contacted

2207: 2205: 1745: 2192: 2190: 1146:

While this work continued, a new solution was introduced.

1033:

could easily solve. They also hoped to gain access to the

2287: 2285: 1571:

The first German airborne sets did not arrive until 1941.

851:

began training the crews on how to best use the systems.

733:

team was hurriedly sent to a prearranged location at the

2494: 2492: 2479: 2477: 2401: 2399: 2323: 2321: 2319: 2317: 2315: 2302: 2300: 2224: 2222: 2220: 741:

Bowen's AI team was sent to a small airfield outside of

2533: 2531: 2416: 2414: 2092:

The Fairey Swordfish Mks. I-IV: Aircraft in Profile 212

1989: 1987: 1985: 1983: 1851: 1849: 1847: 1779: 1777: 1764: 1762: 1760: 1758: 1756: 1754: 1958: 1956: 1943: 1941: 1939: 1866: 1864: 1834: 1832: 1830: 1828: 1729: 1727: 1725: 1289:

at around 10 cm wavelength. Among these were the

1037:, which was several years ahead of their version, the 595:

5 miles needed to close the gap with Chain Home.

390:

In early 1937 the Airborne Group received a number of

1688: 1686: 1613: 1611: 891:

Compact Yagis were mounted to the wing struts on the

554:

The promise of the system was not lost on observers;

915:

it was found the Mk. Is were interfering with naval

158: 150: 142: 134: 126: 116: 106: 98: 90: 79: 64: 56: 2769:, Royal Australian Air Force ASV operator's manual 2638: 643:. In early 1939, Appleton mentioned to Bowen that 267:were in limited supply and priority was given to 843:that had also just started arriving. Meanwhile, 2803:Military equipment introduced from 1940 to 1944 1398:, reducing the complexity of the installation. 1158:In March 1941 they began trying to fit it to a 1101:Ultimately, the countries' parties agreed that 2709:Airborne Maritime Surveillance Radar: Volume 1 1348:The rest of this section concerns the Mk. II. 502:in the Channel, including a combined fleet of 275:by the Germans led to the introduction of the 2240: 2121: 2109: 2008: 436:, along with five pilots stationed at nearby 8: 2645:. Wilfrid Laurier University Press. p. 32: 2358:. Cambridge University Press. p. 146. 451:On its first real test on 17 August, Anson 694:(CRT) that proved suitable for radar use. 162:Type 286, ASE (US Navy), SCR-521 (US Army) 38: 31: 2211: 2196: 2181: 2169: 2157: 2145: 2133: 1311:at 12 miles". This led to contracts with 2755:Long Range Air-Surface Vessel (Radar) R3 1451: 2339: 2291: 2276: 2264: 2252: 1607: 1564: 406:circuit. The new sets were fitted to a 332:Air Member for Research and Development 138:1 to 40 mi (1.6–64.4 km) 2456: 2444: 2432: 2405: 1795: 2798:Military radars of the United Kingdom 2767:ACD 2005; Manual of ASV Mk. II (AUST) 2619:Echoes of War: The Story of H2S Radar 2537: 2522: 2510: 2498: 2483: 2468: 2420: 2378: 2327: 2306: 2228: 2077: 2020: 1993: 1974: 1962: 1947: 1930: 1918: 1906: 1894: 1882: 1870: 1855: 1838: 1819: 1807: 1783: 1768: 1733: 1716: 1704: 1692: 1677: 1665: 1653: 1641: 1629: 1617: 1415:The receiver's output was sent to an 514:successfully detected the battleship 169:Radar, Air to Surface Vessel, Mark II 7: 2390: 2601:. Pen And Sword Military Classics. 2094:. Profile Publications. p. 38. 271:. The capture of a Mk. II-equipped 237:that located the German battleship 2761:Air to Surface Vessels (ASV) radar 943:equipped with Mk. II detected the 183:immediately prior to the start of 25: 535:, receiving very strong returns. 2788:World War II British electronics 2757:, RAF training film on the LRASV 1066:National Research Council Canada 1053:and the initial concepts of the 647:had also been interested in the 2637:Middleton, W E Knowles (1981). 763:(ICI) which produced excellent 365:. For a variety of reasons, an 2670:. Cambridge University Press. 2574:Hanbury Brown, Robert (1991). 2352:Ratcliff, Rebecca Ann (2006). 1513:Research Enterprises (Canada) 485:made the fateful detection of 80: 1: 2553:Bowen, Edward George (1998). 338:at the CH research center at 322:) would be forced to turn to 2706:Watts, Simon (August 2018). 1103:Research Enterprises Limited 761:Imperial Chemical Industries 493:that led to the ASV efforts. 481:. The experimental radar on 446:Royal Aircraft Establishment 228:Research Enterprises Limited 1402:Displays and interpretation 1008:Armstrong Whitworth Whitley 356:Airborne Interception radar 330:, who was at that time the 175:for short, was an airborne 2819: 1553:Searchlight Control radars 1266: 1184: 1116: 1025: 2763:, RAF introduction to ASV 2727:Zimmerman, David (1996). 2712:. Morgan & Claypool. 1539:PMG Research (Australia) 44:ASV Mk. II antennas on a 37: 2733:. McGill-Queen's Press. 2699:10.1049/ip-a-1.1985.0071 2616:Lovell, Bernard (1991). 2580:. Taylor & Francis. 1340:Differences in the Mk. I 426:maritime patrol aircraft 177:sea-surface search radar 2595:Johnson, Brian (1978). 1208:The detector, known as 521:, the aircraft carrier 233:It was Mk. II equipped 2090:Stott, Ian G. (1971). 1412: 1370: 1282: 1197: 1148:Humphrey de Verd Leigh 1135: 980: 972: 900: 823: 718: 619: 528:and the light cruiser 494: 400:intermediate frequency 305: 179:developed by the UK's 57:Country of origin 27:Type of aircraft radar 1409: 1368: 1276: 1194: 1126: 1078:Westinghouse Electric 978: 969: 890: 841:Consolidated Catalina 809: 705: 617: 566:Continued development 470: 299: 1317:Metropolitan Vickers 1187:Metox radar detector 1171:No. 172 Squadron RAF 1039:Automatic Bomb Sight 985:No. 220 Squadron RAF 939:. On 26 May 1941, a 845:Robert Hanbury Brown 833:No. 10 Squadron RAAF 735:University of Dundee 556:Albert Percival Rowe 438:RAF Martlesham Heath 408:Handley Page Heyford 358:", or AI for short. 277:Metox radar detector 2793:World War II radars 2664:Rowe, A.P. (2015). 2279:, pp. 220–237. 2038:Imperial War Museum 1977:, p. 2-2, 2-3. 1421:time base generator 1129:RAF Coastal Command 584:very high frequency 508:RAF Coastal Command 396:push–pull amplifier 210:by an experimental 189:RAF Coastal Command 34: 2667:One Story of Radar 2608:-9781844151028 2241:Hanbury Brown 1991 2122:Hanbury Brown 1991 2110:Hanbury Brown 1991 2059:on 1 December 2007 2009:Hanbury Brown 1991 1413: 1371: 1283: 1198: 1160:Vickers Wellington 1136: 981: 973: 901: 835:was operating the 824: 719: 620: 500:military exercises 495: 306: 273:Vickers Wellington 94:Sea-surface search 49:Consolidated Canso 2687:IEE Proceedings A 2011:, pp. 51–52. 1921:, pp. 89–90. 1822:, pp. 76–77. 1746:Smith et al. 1985 1680:, pp. 37–38. 1656:, pp. 33–35. 1549: 1548: 1419:display with the 1269:ASV Mk. III radar 1132:Liberator GR Mk V 1046:Winston Churchill 863:return flight to 773:Louis Mountbatten 265:cavity magnetrons 256:into deathtraps. 166: 165: 16:(Redirected from 2810: 2744: 2723: 2702: 2681: 2660: 2644: 2633: 2612: 2591: 2570: 2541: 2535: 2526: 2520: 2514: 2508: 2502: 2496: 2487: 2481: 2472: 2466: 2460: 2454: 2448: 2442: 2436: 2430: 2424: 2418: 2409: 2403: 2394: 2388: 2382: 2376: 2370: 2369: 2349: 2343: 2337: 2331: 2325: 2310: 2304: 2295: 2289: 2280: 2274: 2268: 2262: 2256: 2250: 2244: 2238: 2232: 2226: 2215: 2209: 2200: 2194: 2185: 2179: 2173: 2167: 2161: 2160:, p. 67-89. 2155: 2149: 2143: 2137: 2131: 2125: 2119: 2113: 2107: 2096: 2095: 2087: 2081: 2075: 2069: 2068: 2066: 2064: 2055:. Archived from 2048: 2042: 2041: 2030: 2024: 2018: 2012: 2006: 1997: 1991: 1978: 1972: 1966: 1960: 1951: 1945: 1934: 1928: 1922: 1916: 1910: 1904: 1898: 1892: 1886: 1880: 1874: 1868: 1859: 1853: 1842: 1836: 1823: 1817: 1811: 1805: 1799: 1793: 1787: 1781: 1772: 1766: 1749: 1743: 1737: 1731: 1720: 1714: 1708: 1707:, p. 38-39. 1702: 1696: 1690: 1681: 1675: 1669: 1663: 1657: 1651: 1645: 1639: 1633: 1627: 1621: 1615: 1591: 1587: 1581: 1578: 1572: 1569: 1452: 1396:Fairey Barracuda 1281:in January 1943. 1095:cavity magnetron 1057:detailed by the 1035:Norden bombsight 1001:half-power point 954: 941:Fairey Swordfish 893:Fairey Swordfish 876:Bristol Beaufort 837:Short Sunderland 812:Short Sunderland 796:Lockheed Hudsons 723:Bristol Blenheim 692:cathode ray tube 604:corner reflector 560:Tizard Committee 392:Western Electric 375:half-wave dipole 369:with reasonable 235:Fairey Swordfish 212:air-to-air radar 82: 75: 73: 42: 35: 21: 2818: 2817: 2813: 2812: 2811: 2809: 2808: 2807: 2783:Aircraft radars 2773: 2772: 2751: 2749:Other materials 2741: 2726: 2720: 2705: 2684: 2678: 2663: 2657: 2636: 2630: 2615: 2609: 2594: 2588: 2573: 2567: 2552: 2549: 2544: 2536: 2529: 2525:, p. 2-19. 2521: 2517: 2513:, p. 2-17. 2509: 2505: 2501:, p. 2-15. 2497: 2490: 2486:, p. 2-13. 2482: 2475: 2471:, p. 2-10. 2467: 2463: 2455: 2451: 2443: 2439: 2431: 2427: 2419: 2412: 2404: 2397: 2389: 2385: 2381:, p. 2-24. 2377: 2373: 2366: 2351: 2350: 2346: 2338: 2334: 2330:, p. 2-22. 2326: 2313: 2309:, p. 2-21. 2305: 2298: 2290: 2283: 2275: 2271: 2263: 2259: 2251: 2247: 2239: 2235: 2231:, p. 2-20. 2227: 2218: 2210: 2203: 2195: 2188: 2180: 2176: 2168: 2164: 2156: 2152: 2144: 2140: 2132: 2128: 2120: 2116: 2108: 2099: 2089: 2088: 2084: 2076: 2072: 2062: 2060: 2050: 2049: 2045: 2032: 2031: 2027: 2019: 2015: 2007: 2000: 1992: 1981: 1973: 1969: 1961: 1954: 1946: 1937: 1929: 1925: 1917: 1913: 1905: 1901: 1893: 1889: 1881: 1877: 1869: 1862: 1854: 1845: 1837: 1826: 1818: 1814: 1806: 1802: 1794: 1790: 1782: 1775: 1767: 1752: 1744: 1740: 1732: 1723: 1715: 1711: 1703: 1699: 1691: 1684: 1676: 1672: 1664: 1660: 1652: 1648: 1640: 1636: 1628: 1624: 1616: 1609: 1605: 1600: 1595: 1594: 1588: 1584: 1579: 1575: 1570: 1566: 1561: 1447: 1438: 1404: 1384: 1363: 1354: 1342: 1337: 1271: 1265: 1252: 1235: 1189: 1183: 1121: 1115: 1074:radio altimeter 1030: 1024: 964: 952: 885: 872:Blackburn Botha 804: 700: 645:Pye Electronics 641:Edward Appleton 612: 568: 477:, as seen from 465: 457:English Channel 442:ignition system 410:in March 1937. 404:superheterodyne 388: 294: 289: 214:. The original 208:English Channel 71: 69: 52: 28: 23: 22: 15: 12: 11: 5: 2816: 2814: 2806: 2805: 2800: 2795: 2790: 2785: 2775: 2774: 2771: 2770: 2764: 2758: 2750: 2747: 2746: 2745: 2739: 2724: 2718: 2703: 2693:(6): 359–384. 2682: 2676: 2661: 2655: 2634: 2628: 2613: 2607: 2598:The Secret War 2592: 2586: 2571: 2565: 2548: 2545: 2543: 2542: 2540:, p. 209. 2527: 2515: 2503: 2488: 2473: 2461: 2459:, p. 163. 2449: 2447:, p. 161. 2437: 2435:, p. 159. 2425: 2423:, p. 3-3. 2410: 2408:, p. 157. 2395: 2393:, p. 159. 2383: 2371: 2364: 2344: 2342:, p. 239. 2332: 2311: 2296: 2294:, p. 218. 2281: 2269: 2267:, p. 216. 2257: 2255:, p. 215. 2245: 2233: 2216: 2214:, p. 140. 2212:Middleton 1981 2201: 2197:Middleton 1981 2186: 2182:Middleton 1981 2174: 2172:, p. 158. 2170:Zimmerman 1996 2162: 2158:Zimmerman 1996 2150: 2146:Zimmerman 1996 2138: 2134:Zimmerman 1996 2126: 2114: 2097: 2082: 2080:, p. 101. 2070: 2043: 2025: 2023:, p. 2-4. 2013: 1998: 1996:, p. 2-3. 1979: 1967: 1952: 1935: 1923: 1911: 1899: 1887: 1875: 1860: 1858:, p. 2-1. 1843: 1824: 1812: 1800: 1788: 1786:, p. 2-2. 1773: 1771:, p. 2-5. 1750: 1748:, p. 360. 1738: 1721: 1709: 1697: 1682: 1670: 1658: 1646: 1634: 1622: 1606: 1604: 1601: 1599: 1596: 1593: 1592: 1582: 1573: 1563: 1562: 1560: 1557: 1547: 1546: 1543: 1540: 1537: 1534: 1533: 1530: 1527: 1524: 1521: 1520: 1517: 1514: 1511: 1508: 1507: 1504: 1501: 1498: 1494: 1493: 1490: 1487: 1484: 1480: 1479: 1476: 1473: 1470: 1466: 1465: 1462: 1459: 1456: 1446: 1443: 1437: 1434: 1403: 1400: 1383: 1380: 1362: 1359: 1353: 1350: 1341: 1338: 1336: 1333: 1267:Main article: 1264: 1261: 1251: 1248: 1234: 1231: 1203:radar detector 1185:Main article: 1182: 1179: 1117:Main article: 1114: 1111: 1059:MAUD Committee 1028:Tizard Mission 1026:Main article: 1023: 1022:Tizard mission 1020: 963: 962:Long-Range ASV 960: 925:Chain Home Low 884: 881: 803: 800: 787:Bernard Lovell 715:CFB Rockcliffe 699: 696: 611: 608: 567: 564: 464: 461: 387: 384: 293: 290: 288: 285: 226:in the US and 220:Tizard Mission 164: 163: 160: 156: 155: 152: 148: 147: 144: 140: 139: 136: 132: 131: 128: 124: 123: 120: 114: 113: 110: 104: 103: 100: 96: 95: 92: 88: 87: 84: 77: 76: 66: 62: 61: 58: 54: 53: 43: 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 2815: 2804: 2801: 2799: 2796: 2794: 2791: 2789: 2786: 2784: 2781: 2780: 2778: 2768: 2765: 2762: 2759: 2756: 2753: 2752: 2748: 2742: 2740:9780773514010 2736: 2732: 2731: 2725: 2721: 2719:9781643270661 2715: 2711: 2710: 2704: 2700: 2696: 2692: 2688: 2683: 2679: 2677:9781107494794 2673: 2669: 2668: 2662: 2658: 2656:9780889201064 2652: 2648: 2643: 2642: 2635: 2631: 2629:9780852743171 2625: 2622:. CRC Press. 2621: 2620: 2614: 2610: 2604: 2600: 2599: 2593: 2589: 2587:9780750301305 2583: 2579: 2578: 2572: 2568: 2566:9780750305860 2562: 2559:. 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III 1152:searchlight 1119:Leigh Light 1113:Leigh light 860:IFF Mark II 785:Meanwhile, 544:Southampton 532:Southampton 491:Southampton 336:Robert Watt 287:Development 281:ASV Mk. III 249:Leigh light 159:Other Names 130:2.6 μs 2777:Categories 2556:Radar Days 2538:Bowen 1998 2523:Watts 2018 2511:Watts 2018 2499:Watts 2018 2484:Watts 2018 2469:Watts 2018 2421:Watts 2018 2379:Watts 2018 2328:Watts 2018 2307:Watts 2018 2229:Watts 2018 2078:Bowen 1998 2021:Watts 2018 1994:Watts 2018 1975:Watts 2018 1963:Bowen 1998 1948:Bowen 1998 1931:Bowen 1998 1919:Bowen 1998 1907:Bowen 1998 1895:Bowen 1998 1883:Bowen 1998 1871:Bowen 1998 1856:Watts 2018 1839:Bowen 1998 1820:Bowen 1998 1808:Bowen 1998 1784:Watts 2018 1769:Watts 2018 1734:Bowen 1998 1717:Bowen 1998 1705:Bowen 1998 1693:Bowen 1998 1678:Bowen 1998 1666:Bowen 1998 1654:Bowen 1998 1642:Bowen 1998 1630:Bowen 1998 1618:Bowen 1998 1598:References 1445:Production 1382:Mechanical 1305:Philip Dee 1287:microwaves 1240:alternator 1164:Turbinlite 1051:jet engine 883:ASV Mk. II 849:Keith Wood 810:Duxford's 548:Courageous 540:Courageous 525:Courageous 506:ships and 504:Royal Navy 487:Courageous 472:Avro Anson 423:Avro Anson 363:wavelength 310:Chain Home 292:Background 197:Royal Navy 173:ASV Mk. II 146:~5 degrees 127:Pulsewidth 65:Introduced 33:ASV Mk. II 18:ASV Mark I 2391:Rowe 2015 1603:Citations 1411:aircraft. 1105:(REL) in 1076:built by 1068:(NRC) in 802:Early use 757:polythene 698:ASV Mk. I 687:Pye strip 671:destroyer 664:Eindhoven 628:Metrovick 610:New tubes 530:HMS 523:HMS 516:HMS 386:Discovery 319:Luftwaffe 261:microwave 216:ASV Mk. I 154:7 kW 143:Precision 118:Beamwidth 99:Frequency 1542:Mark II 1529:Mark II 1516:Mark II 1503:Mark II 1489:Mark II 1461:Version 1458:Company 1455:Ordered 1361:Antennas 1313:Ferranti 987:against 946:Bismarck 897:Bismarck 831:, where 240:Bismarck 201:Type 286 2063:28 June 1519:10,000 1475:Mark I 1417:A-scope 1352:Signals 1309:Titlark 1297:Sealion 1210:"Metox" 1196:Cross". 1107:Toronto 1090:US Navy 989:HMS L27 951:Bismark 935:in the 759:, from 676:Windsor 656:Philips 588:scatter 573:B-scope 558:of the 448:(RAE). 367:antenna 302:Heyford 245:U-boats 112:400 pps 86:~24,600 70: ( 2737: 2716: 2674: 2653: 2626: 2605: 2584: 2563: 2362: 1545:1,300 1532:7,000 1464:Total 1233:Mk IIA 1070:Ottawa 816:Lucero 658:, the 633:Cossor 518:Rodney 312:(CH), 224:Philco 1559:Notes 1506:3000 1497:1941 1492:3000 1483:1940 1469:1939 1279:MP512 1250:Vixen 1181:Metox 1175:U-502 1173:sank 953:' 779:Kelly 743:Perth 512:K6260 483:K6260 479:K6260 475:K8758 453:K6260 434:K8758 430:K6260 171:, or 151:Power 135:Range 83:built 2735:ISBN 2714:ISBN 2672:ISBN 2651:ISBN 2624:ISBN 2603:ISBN 2582:ISBN 2561:ISBN 2360:ISBN 2065:2019 1478:300 1426:blip 1315:and 1295:HMS 971:III. 933:U-71 874:and 847:and 820:BABS 818:and 777:HMS 750:EKCO 731:AMES 708:RCAF 674:HMS 660:EF50 542:and 489:and 432:and 371:gain 91:Type 72:1940 68:1940 46:RCAF 2695:doi 2691:132 2647:107 713:at 649:BBC 380:EMI 269:H2S 199:'s 108:PRF 81:No. 2779:: 2689:. 2649:. 2530:^ 2491:^ 2476:^ 2413:^ 2398:^ 2314:^ 2299:^ 2284:^ 2219:^ 2204:^ 2189:^ 2100:^ 2036:. 2001:^ 1982:^ 1955:^ 1938:^ 1863:^ 1846:^ 1827:^ 1776:^ 1753:^ 1724:^ 1685:^ 1610:^ 1555:. 1201:a 1061:. 919:. 575:. 428:, 382:. 259:A 203:. 191:, 60:UK 2743:. 2722:. 2701:. 2697:: 2680:. 2659:. 2632:. 2611:. 2590:. 2569:. 2368:. 2067:. 2040:. 955:s 899:. 822:. 354:" 304:. 74:) 20:)

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