<P> The NTRI made minimal changes to the 60 - cm (500 - MHz) Würzburg, mainly converting the oscillator from vacuum tubes to a magnetron . The result was the Type 23 anti-ship, fire - control radar intended for cruisers and larger ships . With the change to a magnetron, the output was approximately halved to a peak - power of about 5 kW; this gave a range of only 13 km for detecting most surface ships . Although the prototype was completed in March 1944, only a few sets were built, and it was never put into serial production . </P> <P> 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 . </P> <P> The prototype for the Type 22 was completed in October 1941; tests showed that it detected single aircraft at 17 km, groups of aircraft at 35 km, and surface ships at over 30 km (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 . </P> <P> 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 . </P>

Jet planes were first developed for use during world war 2 by