page_title: Würzburg radar
section_title: Operational models
hierarchical_section_title: Würzburg radar / Operational models
caption_attribution_description: Deutsch: Details of the Würzburg radar rotating antenna
context_page_description: The low-UHF band Würzburg radar was the primary ground-based gun laying radar for the Wehrmacht's Luftwaffe and Heer during World War II. Initial development took place before the war and the apparatus entered service in 1940. Eventually over 4,000 Würzburgs of various models were produced. It took its name from the city of Würzburg.
context_section_description: Several versions of the basic Würzburg system were deployed over the course of the war. The first, Würzburg A, was operated manually and required the operators to pinpoint the target by maintaining a maximum signal on their oscilloscope display. Since the signal strength changed on its own for various reasons as well as being on or off target, this was inaccurate and generally required the use of a searchlight to spot the target once the radar had settled on an approximate position. Nevertheless, one of the very first Würzburgs in service directly assisted in the shooting-down of an aircraft in May 1940 by orally relaying commands to a flak unit. An experimental Würzburg B added an infra-red detector for fine tuning, but in general these devices proved to be unusable and production was discontinued.
  Würzburg C featured lobe switching to improve aiming accuracy. The C model improved aiming by sending the signal out of one of two slightly off-centre feed horns in the middle of the antenna, with the signal being switched rapidly between the two horns. After slightly delaying the signal from one of the horns, the returns were sent to an oscilloscope display. The result appeared as two closely separated blips which the operator attempted to keep at the same height on the display. This system offered much faster feedback on changes in target position. Changes in signal strength, due to changes in reflection off the target, affected both lobes equally, eliminating common reading errors. An almost identical system was used in the United States's first gun-laying radar, the SCR-268.
  The Würzburg D was introduced in 1941 and added a conical scanning system using an offset receiver feed called a Quirl (German for whisk) that spun at 25 Hz. The resulting signal was slightly offset from the centreline of the dish, rotating around the axis and overlapping it in the centre. If the target aircraft was to one side of the antenna's axis, the strength of the signal would grow and fade as the beam swept across it, allowing the system to move the dish in the direction of the maximum signal and thereby track the target. The angular resolution could be made smaller than the beam width of the antenna, leading to much improved accuracy, on the order of 0.2 degrees in azimuth and 0.3 degrees in elevation. Earlier examples were generally upgraded to the D model in the field.
  Even the D model was not accurate enough for direct laying of guns. In order to provide the system with much greater accuracy, the FuMG 65 Würzburg-Riese (known as the "Giant Würzburg") was developed. Based on the same circuitry as the D model, the new version featured a much larger 7.4 metres (24 ft) antenna and a more powerful transmitter with a range of up to 70 kilometers (43 mi). Azimuth and elevation accuracy was 0.1-0.2 degrees, which was more than enough for direct gun-laying. The system was too large to be carried on a truck trailer and was adapted for operation from a railway carriage as the Würzburg-Riese-E, of which 1,500 were produced during the war. The Würzburg-Riese Gigant was a very large version with a 160 kW transmitter, which never entered production.
  A Würzburg system at Bruneval on the coast of France was captured by British Paratroopers in Operation Biting, while Operation Bellicose bombed the suspected Würzburg radar factory. The Operation Hydra bombing of Peenemünde did not affect the nearby Giant Würzburg at the Lubmin guidance and control station used for the V-2 rocket.
caption: Details of the rotating quirl dipole. The flat disk on the left, the reflector, faces the target. The rotating dipole broadcasts toward the reflector, which reflects the signal to the right. The main antenna dish would be positioned out of frame on the right, where it would focus the signal into a narrow beam facing the target.
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