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BELL SYSTEM TECHNICAL JOURNAL 



have seen extensive use in many forms of pulsed radar systems. They have 

 also served as the basis for much of the subsequent magnetron design work. 



16. Magnetrons for Wavelength near 10 Centimeters— 

 200 Kilowatts to 1 Megawatt 



16.1 The 720A-E Magnetrons: A natural outgrowth of the early mag- 

 netron experimentation was the effort to generate higher power. Since the 

 earliest magnetrons were unstrapped there was much to be hoped for in 



Fig .61 — An internal view of a 706AY-GY magnetron (150 k\\., '-^3000 mc/sj. Note 

 the type of wire strapping [compare Fig, 24(a)] and the simple coaxial output circuit. 



improved efficiency. Higher power magnetrons would have to be designed 

 to operate at voltages above 20 kv. and currents of greater than 50 amps. 

 To accomplish these objectives, the interaction space was enlarged, in some 

 designs involving a greater number of resonators, and the anode length 

 increased by two or even three times. .Although it was possible to develop 

 over 200 kw. with magnetrons of eight, ten, and twelve resonators, efficiencies 

 were poor, seldom exceeding 20 per cent at maximum loading. This was 

 even poorer than unstrapped 10 cm. magnetrons hke the 706A-C. The 

 reduction in mode frequency separation attendant upon increases in anode 

 length and number of resonators was later found to be the cause. 



Following their first use in the 718AY-EY magnetrons, straps were in- 



