RCN, the first sets were not available until July 1943. The RX/C incorporated many of the characteristics of the SW sets, but had a PPI display and a parabolic-reflector antenna. Further sets were produced by the REL and used throughout the war. The Admiralty in Great Britain asked about Canada's interest and capability in manufacturing 3-cm magnetrons. This led to the development of a 3-cm device by the NEC and a full 3-cm (10-GHz) radar for small crafts. In May 1942, the British Admiralty gave a formal purchase order for these developments. The set was designated Type 268 (not to be confused with the SCR-268 from the U.S. Signal Corps), and was particularly designed to detect a submarine snorkel. With extensive testing and subsequent changes, full-scale production did not start until December 1944. About 1,600 Type 268 sets were manufactured before the end of the war. While the Canadian Army was basically satisfied with the 200-MHz CD systems, it did ask for an improvement to 10-cm operation. Since the Microwave Section was then well experienced in these systems, they easily provided a design. Before even a prototype was built, the Army gave an order to the REL for a number of sets designated CDX. Production started in February 1943, but only 19 sets were actually delivered with 5 of these going to the USSR. In the spring of 1943, German submarines started operating just outside the Saint Lawrence Seaway – the primary ship route from Canada to Great Britain. To counter this, the Royal Canadian Air Force (RCAF) asked that 12 sets of a long-range microwave system be built. A magnetron producing 300 kW at 10.7 cm (2.8 GHz) was developed by the firm NEC. For radiating a narrow horizontal beam to sweep the sea surface, a slotted antenna 32 by 8 feet in size was designed by William H. Watson at McGill University. The system was designated MEW/AS (Microwave Early Warning Anti Submarine). The transmitting and receiving equipment was located behind the antenna, and the assembly could be rotated at up to 6 RPM. The controls and PPI display was in a nearby fixed building. This could detect targets at up to 120-miles (196-km) range. A second version, designed for detecting high-flying aircraft, was designated MEW/HF (Height Finding). In this, the power could be switched to a smaller, rotating antenna that gave a narrow vertical beam. The RCAF put