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netrons with a tunable equivalent necessitated a tuning range which was 

 found to be unattainable with the scheme used in the 4J42 and 4J51 mag- 

 netrons. Two tunable replacements employing the "tuned segment" type 

 of tuning, each spanning half the band, were constructed as "insurance" 

 should the efforts to develop a single replacement having the required range 

 fail. However, it was found that by tuning the straps as has been de- 



Fig. 55 — A view of a cut-away 4J51 tunable magnetron (275 kw., 900 to 970 mc/s). 

 Note the tuning member consisting of two concentric rings which are moved up and down 

 in the grooves in the segments of the anode structure. The details of the tuning drive 

 mechanism, including the flexible vacuum diaphragm, the axial screw, the nut and ball 

 bearing, and the gear drive are to be seen. The resonator system is strapped on the end 

 not seen in the figure. 



scribed in PART I a single tunable magnetron for the entire 4J21-30 series 

 covering the band from 1220 to 1350 mc/s could be provided. An e.xternal 

 view of the resulting magnetron, coded the 5J26, is shown in Fig. 57 and 

 an internal view in Fig. 58. 



As can be seen in Fig. 58, the 5J26 magnetron includes radical departures 

 in design in addition to the tuning scheme. Slot type resonators are used 

 in the resonator system, and the anode and cathode diameters, as well as 

 their ratio, are considerably larger than those used in previous designs for the 

 same operating voltage and magnetic field. These features of the design 



