> Ordinary magnetrons had indeed been around for a while; they were invented in > 1920. The British invention was the _cavity magnetron_, a quite different > beast; it was kind of a cross between a magnetron and a klystron, with the > best features of each.
The cavity magnetron was invented by a lot of people (Soviet, Japanese, German, Swiss, United States, and I think the Danish*), just like radar itself. Most of these inventors fell to the wayside, because the cavity magnetron just was not a useful device. Most of these inventors tried to use the cavity magnetron as a CW oscillator, and in that mode, they are basically awful tubes. Randall and Boot ("the British") invented the pulse operation of the cavity magnetron - a way to basically abuse the tubes but get pulses magnitudes more powerful than previously done. This, of course, was the key to microwave radar. * much of this original research was not secret, just ignored. RCA's "split anode tank magnetron" was even completely described in one of their tech journals. -- Will