Dorking & District Radio Society

The History of the Magnetron from WW2 Radar to the Kitchen - 22 January 2019

Mike Underhill G3LHZ

The invention of the High Power Cavity Magnetron in 1940 by John Randall and Harry Boot at the University of Birmingham has changed the face of the world. It certainly changed the course of, and significantly shortened World War 2 by providing a superior high frequency (3 GHz), high power (kW) radar oscillator. Although the magnetron has since been superseded by other devices for some radar applications, the use of magnetrons within microwave ovens has changed the face of the modern kitchen across the world and arguably initiated a cultural revolution that may never be reversed. It is estimated that there are currently one billion magnetrons in use worldwide. But has the magnetron any future or will it be overtaken by other competitive technology? For example, will it be replaced by LDMOS devices (laterally diffused metal oxide semiconductors) as used in the latest kilowatt amateur solid-state linear amplifiers. (These are now available in the HF to UHF bands and are much easier to lift!)

Mike passed his RAE at the age of 14 in 1953 and the Morse exam in 1955 obtaining his full licence G3LHZ in 1956, and joining the RSGB in 1957. He has been reasonably active on the air ever since, continuously on the BAD-net (Billingshurst and District-net) at 1000 local-time on 3722 kHz. Mike is a founding member of the Crawley Amateur Radio Club (CARC) and was the winning NFD operator on 23 cm for CARCRATS in 2012 with G3GRO and single operator in 2014.  He has given many talks to clubs mainly but not exclusively on small loops; this is the 56th since 1998. Currently Mike is very busy on some interesting basic physics and electro-magnetic research on Antennas and Propagation, a small part of which relates to and springs from Small Transmitting Loops! Mike has been to the annual Hamvention in Dayton, Ohio about four times and is a 'regular' (seven or eight times) at the International Amateur Radio Exhibition held annually in Friedrichshafen, Germany.

Mike's career included 25 years at Philips Research Labs, rising to Divisional Head, six years as Technical/Engineering Director for MEL the Thorn-EMI in Crawley, and 13 years as Professor of Electronics, Head of Department and Dean of Engineering at the University of Surrey. Overlapping this, he was for 10 years Founder and Research Director of Toric Limited, an SME supplying 'embedded-jitter-suppression' solutions to the semiconductor industry. Underhill Research Limited is a very busy semi-retirement activity involving research and presenting conference papers around the world (Turin and California last year.)