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BELL SYSTEM TECHNICAL JOURNAL 



of the high voltage gradient in air which had existed at the small diameter 

 tungsten rod resulted. 



In Fig. 64 is shown a typical performance chart for the 720A-E series. 

 Other performance data are given in Table II. In Fig. 44 is shown one of 

 the 720A-E magnetrons mounted in its magnet. 



30 40 50 60 



DC CURRENT,!, IN Ar^PERES 



Fig. 64 — A typical performance chart of the 720A-E magnetrons ('^2800 mc/s). 



In the use of the 720A-E on line type modulators the difficulty with what 

 was then called voltage "overshoot" was first encountered. It is the result 

 of the finite buildup time for the RF oscillation during which the pulse 

 voltage rises to values higher than required for tt mode operation. It is 

 particularly aggravated on line type modulators for which the magnetron, 

 before it oscillates and draws current, presents a mismatch to the Hne net- 

 work causing the voltage to rise to a much higher value. The difficulty was 



