Recollections of pre-world war II magnetrons and their applications

The magnetron development work at Westinghouse Research Laboratories in the years 1929 to 1934 and at RCA from 1934 to 1938 is described. The Westinghouse work led to internal-circuit magnetrons with powers on the order of 1W at 9-cm wavelength, and detectable power down to 1.6 cm. A complete microwave relay system using searchlight mirrors was built and demonstrated at the Chicago "Century of Progress" exhibition in 1933-1934. Later work at RCA was directed to longer wavelength in the 60-cm range, where powers of 100 W were obtained. These were CW tubes: the need for pulsed tubes for radar was never disclosed to the tube designers at that time.