Although the prototype was completed in March 1944, only a few sets were built, and it was never put into serial production. Japan Radio Company (JRC) had long worked with the NTRI in developing magnetrons. In early 1941, JRC was given a contract by NTRI to design and build a microwave surface-detection system for warships. Designated Type 22, this used a pulse-modulated, 10 cm (3.0 GHz) magnetron with water-cooling and producing 2 kW peak-power. The receiver was a super-heterodyne type with a low-power magnetron serving as the local oscillator. Separate horn antennas were used for transmitting and receiving. These were mounted on a common platform that could be rotated in the horizontal plane. Since it was Japan's first full set using a magnetron, Yoji Ito was made responsible and gave it special attention. The prototype for the Type 22 was completed in October 1941; tests showed that it detected single aircraft at , groups of aircraft at , and surface ships at over (depending on the height of the antenna above the sea). The first Japanese warships with microwave radar received these in March 1942, and by late 1944, microwave radar was widely in use on surface vessels and submarines; about 300 Type 22 sets were built. With the poor range of the Type 23 (the Würzburg copy), development was started on three microwave systems for fire-control applications. The Type 31 operated at 10 cm (3 GHz) and, like the Würzburg, used a common parabolic reflector. While the prototype could detect larger ships at up to 35 km, it was not completed until March 1945 and was never placed into production. The Type 32 was another 10 cm system, this one having separate square-horn antennas. Detection range for large ships was about 30 km. It became operational in September 1944, and some 60 sets were produced. Type 33 was still another 10 cm set; this one used separate round-horn antennas. The prototype was completed in August 1944, but like the Type 23, detection range was only 13 km and it was not put into production. The Imperial Navy had a large number of aircraft. It was almost a year after the start of the war, however, before the first airborne set was developed at the Oppama Naval Air Technical Depot (ONATD). Initially designated Type H-6, with a number of experimental sets built, this was eventually produced as the Type 64