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ID = 15817
Great Britain (UK)
Brand: GEC, General Electric Co Ltd., GENALEX; London
Tube type:  Pulse magnetron   Text 
Identical to E1189 = NT98 = D-160052 = REL3D = NTA98
First Source (s)
29.Jun.1940 : -- Original-techn. papers. Megaw, 1946 IEEE article
Predecessor Tubes E1189_Prototype  
Successor Tubes E1198   Q85033   706A   1259M   D-160052  

Was used by Radar
Filament Vf 6 Volts / If 1.2 Ampere / Half indirect

Eight segments pulsed magnetron. Typical specs: 12KW peak at 9.5cm, with 8.5KV.
Starting form the early prototype assembled by Randall and Boot at the Birmingham University, E.C.S. Megaw at GEC designed the E1189, which was the first pulsed multicavity magnetron to be produced. In the early prototypes, up to the S/N 11, the anode had six cavities, according to some tales machined using the chamber of a Colt revolver as drilling template.
The early design was modified to use an oxide coated cathode and, starting from the sample No. 12, the anode had 8 cavities.
The same sample No. 12 was brought in August 1940 to North America by the Tizard mission and its design details were disclosed to Western Electric and to Raytheon in U.S. and to R.E.L. in Canada, originating a wide variety of types.
E1189 was used in the Naval radar Type 271, operational since July 1941. The tube was standardized by the Admiralty as NT98, AP W2510.

The development of the E1189 magnetron at GEC can be read at this link.

Information source Taschenbuch zum Röhren-Codex 1948/49   
-- Original prospect or advert   Callick, Metres to Microwaves
-- Original-techn. papers.

E1189: Manufacturer's Literature
Emilio Ciardiello

Collection of




The decision for the new low-field eight-cavity variant was taken on 17 July 1940. Megaw launched a rush production of four samples. Two of them were sealed and serialized as E1189 No. 12 and 13. Two more samples were likely used to perform laboratory tests. The first one, assembled without the radiator and sealed with wax while continuously pumped, was likely operated on the bench since the end of July 1940, some days before the 8-slot Megaw's design was approved on 6 August 1940 and well before the No. 12 sample started its trip to America.

The first sample made by Megaw at GEC was six-segment, machined anode block being supplied by Birmingham. Cathode was a spiral wound thoriated-tungsten filament. It started operate on 29 June 1940, giving about 1 kW pulses at 1000 Oersted magnetic field. Wavelength was about 9.8 cm. Power pulses raised to about 10 kW at 1400 Oersted in the polepieces of an electromagnet.

From No.12 E1189 was made to the new low-field eight-cavity Megaw's design. The diameter of oxide-coated cathode was increased to 6 mm. At about 1000 Oersted, in the polepieces of a 6 lbs. magnet, it was capable of delivering 5 kW minimum, 10 kW typical pulses. S/N 12 was brought to America by the Tizard Mission and its design was unvealed to Bell, Raytheon and MIT Radiation Lab. S/N 13 was used by Megaw to characterize it. Source: Megaw's notes

Starting from S/N 2 and up to S/N 11, E1189 was still six-cavity but cathode was half-indirect, with a 4.5 mm diameter oxide-coated nickel cylinder. E1189 S/N 2 was completed and operated at the same time of the sample S/N 1, same results. Few days after the middle of July, likely on 17, the sample No.2 went to the group of Dee at TRE. Nine more samples were made of this variant, likely completed around the end of July and August 1940.

Forum contributions about this tube
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Early Magnetron Development - E1189 (E1189)
Roy Johnson

The following extract from Metres to Microwaves - Callick, gives some of the background to the developments that lead to a practical device capable of mass production in England and the USA.

After Randall and Boot's demonstration of their 6-cavity 10 cm magnetron,
which was fitted with a small diameter tungsten filament cathode and therefore
basically a device for continuous operation, Megaw and his group at GEC made
essential and fundamental changes to the original Birmingham design, and in
mid-1940 developed E1189, the first magnetron suitable for use as a radar
transmitter*. This had a large diameter oxide cathode with end discs, similar to
one used earlier by H. Gutton of SFR in his 8- and 12-segment interdigital
magnetrons. Some years previously, Megaw, who was in close contact with
Gutton, had identified back bombardment of the cathode and the importance of
-secondary emission as the major source of operating current. He had also
ventured the opinion that magnetrons would operate efficiently with cathodes
significantly greater in diameter than the tungsten filaments and small spirals in
common use at that time. It was Gutton who demonstrated the manyfold increase
in power which could be obtained by replacing a tungsten spiral by a large oxide
cathode, and that cathodes of this type could withstand operation with very high
voltages. Megaw himself acknowledges the great importance of Gutton's innovation,
which was the key to development of multicavity magnetrons giving peak
power outputs from ten to several hundred kilowatts. Without the invention of
'strapping' by J. Sayers of Birmingham University and the refinement of this
technique by S. Devons ofTRE , who originated 'strap setting', the multicavity
magnetron would have continued to be inherently unstable in frequency and
difficult to operate. The addition ofstraps also increased the efficiency and power
output by many times. Without them, development of the 'megawatt' S-band
magnetron would have been delayed by many years. The addition of straps also
increased productivity in manufacture. Later on, B.V. Rollin of the Clarendon
Laboratory, who had concentrated on designs for wavelengths down to 1.25 cm,
invented the 'rising sun' resonator system. This required no straps, and so was
much easier to fabricate than the ring-strapped system. (The rising sun design
was also used by Columbia University, New York in their X- and K-band
magnetrons. It is almost certain that they originated their own design independently)

• In a letter to Dr. Megaw's secretary shortly after his death in 1956, Sir Edward Appleton, who
in 1940 was a member of the Committee for the Scientific Survey of Air Defence (the 'Tizard'
Committee), wrote 'Those who were in the business know how much the practical development
ofthe cavity magnetron - the development that made it something that could go into operational
use - was due to Dr. Megaw.' [The Tizard Committee reported to and made recommendations
for action by the Subcommittee on Air Defence Research which reported to the Committee of
Imperial Defence.]

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