MAGNETRON AS GENERATOR OF CENTIMETER WAVES 289 



strap capacitance of the single pair of rings to approximately twice that of 

 one pair in the 728A-J. The tuning scheme is the same as that used in the 

 4J42. It may be seen in the photograph of a cut-away model in Fig. 55. 



The output circuit of the 4J51 incorporated the broad band transformer 

 properties developed for the output circuit of the 4J21-30 series. This 

 necessitated a larger loop size in the 4J51 than was used in the 728A-J. 



Fig. 54— The 4J51 tunable magnetron (275 lew., 901) to 970 mc/s)— the tunable re- 

 placement for the 728A-J magnetrons. 



These features may be seen in Fig. 55. The output circuit was designed for 

 coupling to a matched load line. 



Table I includes relevant data on the 4J51 magnetron. In Fig. 56 are 

 shown power output and mode frequency tuning curves for the magnetron. 

 Fig. 56 may be taken as representative of the type of tunable magnetron 

 in which the intersegment capacitance of the resonator system is varied. 

 The frequency range is limited by the crossing of the t mode frequency 

 cur\-e by those of other modes. The power output is reduced appreciably 

 at the crossing point of the n = 3 mode component. Throughout its tuning 

 range, indicated in Fig. 56, the 4J51 magnetron operates as well or better 

 than its fixed frequency predecessors. 



14.4 The 5J26 Maguetron: Replacement of the 4J21-30 series of mag- 



