In June of 1940, Eric Stanley Megaw, based on
experiments with Generel Electric Company E821 glass magnetron, had designed a
cavity magnetron in England which worked on 10 cm and became available for
aircraft interception. This magnetron was air cooled and J. Randall and H.
Boot turned it into a water cooled unit. The magnetron became the
heart of the H2S radar which also used a PPI CRT installed in British bombers. The cavity magnetron had a
substantial increase in performance over other magnetrons of its time and it
played a substantial role in the history of radar.
|Schematic of the classic magnetron transmitter by Hull.
||Habann Tube split into four segments.
Because Randall and Boot built a cavity magnetron, the claim that the British invented radar is made. This is simply not true. The book
"History of Communications-Electrics in the United States Navy", 1963, on pg. 447 claims, "British scientists took an American invention,
the cavity magnetron, and improved it to where it was . . . ". "This device was invented by Dr. A.W. Hull, of the General Electric Co., in
1921." However, Dr. H.E. Hollmann's book
Physik und Technik der ultrakurzen Wellen, Erster Band, 1935," Chapter 4 deals with the history of the magnetron in its many variations. Hollmann
states that Greinacher in Germany first discussed the theory of the magnetron and then Hull further developed it. See the schematic of the Hull
Magnetron transmitter taken from Hollmann's book. Also in 1921, a German physicist by the name of Habann developed a split tube magnetron generator
working on a wavelength of 3 cm. Habann is generally given the credit of being the inventor of the magnetron from which the cavity magnetron evolved.
Furthermore, in 1935, Dr. H.E. Hollmann filed a patent on the multicavity magnetron well ahead of Randall and Boot's work. Click here to see
this and his other magnetrons.
All of the
patents filed by Telefunken in Germany were also filed in the USA. These were
most of H. E. Hollmann's patents, W. Runge, director of Telefunken, patents
and tens of thousands of other relating radar patents. These patents were available to
all General Electric Co., GEC, technical personal. You
see, Telefunken owned the German company, AEG which was allied with GEC and
traded all patents with GEC. In this way, most of the German radar secrets, were available to the Allies. The Allies, England
and America primarily, used these patents to develop their radar
Unlike the disclosure of the German radar
secrets, the British worked in the strictest of confidence and secrecy during WWII and
developed the H2S airborne radar which used a magnetron and a PPI. This unit
worked well and could identify targets on the ground for night and all weather
In February 1943, a Stirling bomber with the H2S radar was shot down near
Rotterdam and the radar was found by the Germans. The
Germans tested this radar. They built a improved unit by June of 1943 called the LMS 10 "Berlin."
During the war, the British worked closely with the US to
improve their radar systems and radar jamming methods.