Deleted member 1487
Because their work was quite behind IOTL until they had a technology exchange with Germany in 1940-1:Why not have the Japanese follow up their own actual research instead?
https://en.wikipedia.org/wiki/Yoji_Ito#VHF
Move up Ito's trip to 1938:Germany had radar by 1938 and installed air intercept and gunfire surface radars on their ships by 1940. Lets have Japan get German sets for all its aircraft carriers by the end of 1940.
In late 1940. Commander Ito led a technical-exchange mission to Germany. Fluent in the German language and holding a doctorate from Dresden Technische Hochschule, he was well received. Staying several months, he became aware of their pulse-modulated radio equipment for detecting and ranging, and immediately sent word back to Japan that this technology should be incorporated in the NTRI-JRC effort. On August 2, 1941, even before Ito returned to Japan, funds were allocated for the initial development of a pulse-modulated Radio Range Finder (RRF – the Japanese code name for a radar).
The Germans had not yet developed a magnetron suitable for use in such systems, so their equipment operated in the VHF region. At the NTRI, they followed the Germans and built a prototype VHF set operating at 4.2 m (71 MHz) and producing about 5 kW. This was completed on a crash basis, and in early September 1941, the set detected a bomber at a range of 97 km (61 mi). The system, Japan’s first full radar, was designated Mark 1 Model 1 and quickly went into production.[6]
It would help too if Ito shared his work on the magnetron in the exchange to get the Germans working in that direction and maintain the technology exchange into and during the war.