MAGNETRON AS GENERATOR OF CENTIMETER WAVES 



291 



resulted from a systematic study of the causes of and possible cures for the 

 maximum current Hmitation encountered in long wavelength magnetrons. 

 The difficulty had been particularly noticeable in the 4J21-30, which on 



05 1.0 1. 



TUNER POSITION IN 



5 2.0 2.5 3.0 3.5 



MM. (MEASURED FROM MAXIMUM INTRUSION) 



Fig. 56— Typical experimental curves of power output and mode frequency variation 

 with tuner position in the 4J51 magnetron. The following points of interest are to be 

 noted: the relatively more rapid tuning for modes of small n than for the tf mode (« = 4); 

 the drop in out[)ut power at the coincidence of the frequencies of the tt mode and one of the 

 components of the n = 1 mode; the limitation on the tuning range in the tt mode imposed 

 by the crossing of mode frequency curves of other modes; the fact that the n = 1, 2, and 

 3 modes are doublets and the tt mode a singlet. 



hard tube modulators were able to pass the required current before x mode 

 failure with little margin. For some reason the performance of the early 

 experimental models of the tunable replacement was considerably inferior 

 in this respect and would not meet the specifications for which the magnetron 

 was being designed. Thus a study of the phenomenon was imperative. It 



