of 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 The resulting signal was slightly offset from the centreline of the dish, rotating around the axis and overlapping it in the center. 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 beamwidth 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 antenna and a more powerful transmitter with a range of up to . 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. Countermeasures As the radar was one of the most common in German use, the British spent considerable effort countering the system during the war. In February 1942, a Würzburg-A system at Bruneval on the coast of France was captured by British Paratroopers in Operation Biting. Several key components were returned to the UK, which allowed the operational parameters of the system to be accurately determined. This led to the modification of existing transmitter systems to produce the "Carpet" system that broadcast noise on the frequencies used by particular Würzburg systems. Several updated versions of Carpet were introduced; Carpet II was the primary UK version while Carpet III was its US-built