The earliest form of magnetron was described by Albert W. Hull of GE in 1921. Hull’s magnetron is simply a diode with a cylindrical anode. It was described publicly in the AIEE Journal in 1921.
W. Pistor published a paper dealing with the reception of ultra short waves in 1930 and in 1935 the travelling wave microwave oscillator (a type of early magnetron) had been invention by O. Heil and A. Heil.
In Britain, the possibility of using radar waves to detect aircraft arose in the early 1930s and work on magnetrons started at the GEC Hirst Research Center (Wembley) in 1931.
A highly important contribution was the invention of the cavity magnetron in November 1939 by John Randall and Harry Boot at the University of Birmingham.
On 21 February 1940, Boot and Randal verified their first microwave transmission with their prototype magnetron. Within days, they were generating an astonishing 500 W of output power at over 3 GHz, an achievement almost two orders of magnitude beyond the previous state of art.
Their invention enabled the development of radar systems with sufficient spatial resolution to distinguish enemy aircraft from those of the Allies.
Invention of magnetron
