Newer techniques of VHF radio communications and direction-finding may additionally be used, but all of those methods had been highly vulnerable to enemy interception. At the NTRI, Yoji Ito proposed that the UHF signal from a magnetron might be used to generate a very narrow beam that would have a greatly decreased likelihood of enemy detection.
In November 1941, the primary manufactured RRF was placed into service as a land-based early-warning system at Katsuura, Chiba, a city on the Pacific coast about a hundred km from Tokyo. The detection range was about one hundred thirty km for single aircraft and 250 km for groups. In late 1940, Japan arranged for 2 technical missions to visit Germany and trade details about their developments in navy expertise.
There isn’t any indication that both...Read More