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ASV Mark II radar
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ASV Mark II radar
Radar, Air to Surface Vessel, Mark II, or ASV Mk. II for short, was an airborne sea-surface search radar developed by the UK's Air Ministry immediately prior to the start of World War II. It was the first aircraft-mounted radar of any sort to be used operationally. It was widely used by aircraft of the RAF Coastal Command, Fleet Air Arm and similar groups in the United States and Canada. A version was also developed for small ships, the Royal Navy's Type 286.
The system was developed between late 1937 and early 1939, following the accidental detection of ships in the English Channel by an experimental air-to-air radar. The original ASV Mk. I 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 Tizard Mission 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 Philco in the US and Research Enterprises Limited in Canada, with over 17,000 produced for use in the US alone.
It was Mk. II equipped Fairey Swordfish that located the German battleship Bismarck in heavy overcast skies, torpedoing her and leading to her destruction the next day. Mk. II was only partially effective against the much smaller U-boats, especially as the signal faded as the aircraft approached the target and they would lose contact at night. To close the gap, the Leigh light 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, night-time U-boat interceptions became common, and turned the German ports in the Bay of Biscay into death-traps.
A microwave-frequency ASV radar, ASVS, was under development since 1941, but the required cavity magnetrons were in limited supply and priority was given to H2S. The capture of a Mk. II-equipped Vickers Wellington by the Germans led to the introduction of the Metox radar detector 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, ASV Mk. III, was rushed to service, replacing the Mk. II beginning in 1943. Mk. II remained in use throughout the war in other theatres.
Early during the development of the first British radar system, Chain Home (CH), Henry Tizard became concerned that the CH system might become so effective that the German air force (Luftwaffe) would be forced to turn to night bombing. If so, this would present a new problem for Britain, since CH alone couldn't provide the accuracy its fighter pilots needed to target bombers at night. After all, CH could locate an invading plane to no better than about 1 mile (1.6 km) in range, couldn't determine its bearing accurately and was even worse at estimating its elevation. Combined with the fact that a fighter pilot at night could see no farther than about 1,000 feet (300 m), this meant there would be a significant coverage gap for the enemy to exploit. He concluded that to be effective against night bombing, British pilots would need additional guidance to supplement Chain Home. Tizard wrote a memo on the topic on 27 April 1936[citation needed] and sent it to Hugh Dowding, who was at that time the Air Member for Research and Development, and copied Robert Watson-Watt at the CH research center at Bawdsey Manor in Suffolk.
Over meetings Watson-Watt held with his research team in Orford at the local Crown and Castle hotel, they ultimately agreed that the best solution to the problem was to develop a small radar that could be mounted in an aircraft. The idea was that if the CH system could get a fighter to the general area of the enemy plane — within a mile or so — then the aircraft's own radar could be used guide it close enough for the pilot to see the plane visually and target it. Edward "Taffy" Bowen asked to take on the project, and formed a small team in August 1936 to consider the problem. They gave the concept the name RDF Project 2, or simply RDF 2. It would later come to be known as airborne radar, and would soon evolve into the related fields of aircraft interception (AI) radar and aircraft-to-surface-vessel (ASV) radar. (Meanwhile, the technology of Chain Home, originally called RDF, was renamed RDF 1.)
The major problem faced by the Airborne Group was the problem of wavelength. For a variety of reasons, an antenna with reasonable gain has to be on the same order of length as the wavelength of the signal, with the half-wave dipole 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 wavelengths, eventually settling on a set working at 6.7 m, based on an experimental television receiver built at EMI.
In early 1937 the Airborne Group received a number of Western Electric 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 push–pull amplifier 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 intermediate frequency portion of a superheterodyne circuit. The new sets were fitted to a Handley Page Heyford in March 1937.
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ASV Mark II radar
Radar, Air to Surface Vessel, Mark II, or ASV Mk. II for short, was an airborne sea-surface search radar developed by the UK's Air Ministry immediately prior to the start of World War II. It was the first aircraft-mounted radar of any sort to be used operationally. It was widely used by aircraft of the RAF Coastal Command, Fleet Air Arm and similar groups in the United States and Canada. A version was also developed for small ships, the Royal Navy's Type 286.
The system was developed between late 1937 and early 1939, following the accidental detection of ships in the English Channel by an experimental air-to-air radar. The original ASV Mk. I 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 Tizard Mission 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 Philco in the US and Research Enterprises Limited in Canada, with over 17,000 produced for use in the US alone.
It was Mk. II equipped Fairey Swordfish that located the German battleship Bismarck in heavy overcast skies, torpedoing her and leading to her destruction the next day. Mk. II was only partially effective against the much smaller U-boats, especially as the signal faded as the aircraft approached the target and they would lose contact at night. To close the gap, the Leigh light 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, night-time U-boat interceptions became common, and turned the German ports in the Bay of Biscay into death-traps.
A microwave-frequency ASV radar, ASVS, was under development since 1941, but the required cavity magnetrons were in limited supply and priority was given to H2S. The capture of a Mk. II-equipped Vickers Wellington by the Germans led to the introduction of the Metox radar detector 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, ASV Mk. III, was rushed to service, replacing the Mk. II beginning in 1943. Mk. II remained in use throughout the war in other theatres.
Early during the development of the first British radar system, Chain Home (CH), Henry Tizard became concerned that the CH system might become so effective that the German air force (Luftwaffe) would be forced to turn to night bombing. If so, this would present a new problem for Britain, since CH alone couldn't provide the accuracy its fighter pilots needed to target bombers at night. After all, CH could locate an invading plane to no better than about 1 mile (1.6 km) in range, couldn't determine its bearing accurately and was even worse at estimating its elevation. Combined with the fact that a fighter pilot at night could see no farther than about 1,000 feet (300 m), this meant there would be a significant coverage gap for the enemy to exploit. He concluded that to be effective against night bombing, British pilots would need additional guidance to supplement Chain Home. Tizard wrote a memo on the topic on 27 April 1936[citation needed] and sent it to Hugh Dowding, who was at that time the Air Member for Research and Development, and copied Robert Watson-Watt at the CH research center at Bawdsey Manor in Suffolk.
Over meetings Watson-Watt held with his research team in Orford at the local Crown and Castle hotel, they ultimately agreed that the best solution to the problem was to develop a small radar that could be mounted in an aircraft. The idea was that if the CH system could get a fighter to the general area of the enemy plane — within a mile or so — then the aircraft's own radar could be used guide it close enough for the pilot to see the plane visually and target it. Edward "Taffy" Bowen asked to take on the project, and formed a small team in August 1936 to consider the problem. They gave the concept the name RDF Project 2, or simply RDF 2. It would later come to be known as airborne radar, and would soon evolve into the related fields of aircraft interception (AI) radar and aircraft-to-surface-vessel (ASV) radar. (Meanwhile, the technology of Chain Home, originally called RDF, was renamed RDF 1.)
The major problem faced by the Airborne Group was the problem of wavelength. For a variety of reasons, an antenna with reasonable gain has to be on the same order of length as the wavelength of the signal, with the half-wave dipole 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 wavelengths, eventually settling on a set working at 6.7 m, based on an experimental television receiver built at EMI.
In early 1937 the Airborne Group received a number of Western Electric 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 push–pull amplifier 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 intermediate frequency portion of a superheterodyne circuit. The new sets were fitted to a Handley Page Heyford in March 1937.
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