MAGNETRON AS GENERATOR OF CENTIMETER WAVES 283 



magnetron is the choke or contact free coupling to the load coaxial. The 

 general t}-pe of design used in j^rcvious magnetrons was followed here. The 

 transformation from the load coaxial to the coaxial which breaks into the 

 resonator at the coupling loop was made by use of a tapered line in which 

 the characteristic impedance was kept constant. The proper loading was 

 accomplished by adjustment of the loop size. It was found possible to 

 achieve a sutTiciently low loaded Q in this way within the bounds of a satis- 

 factory- geometrical arrangement. Each of these design procedures was 



Fig. 51— An internal view of a 4J21-30 magnetron (600 k\v., ^^1280 mc/s). Of special 

 interest are the recessed double ring straps and the output circuit in which the character- 

 istic impedance of the coaxial line from loop to load is approximately constant. 



carried out by C\V measurement of impedance, looking into a model through 

 the output circuit. Special models of the tapered line and choke coupler 

 were also studied. 



When operating magnetrons were constructed, except for minor changes, 

 no redesign was necessary-. The first working models performed satis- 

 factorily at the required pulse voltage, current, magnetic field, power out- 

 put, and pulling figure. It was possible to get more than 750 kw. output at 

 better than 50 per cent ei!iciency from these magnetrons. 



An external view of the final design may be seen in Fig. 50 and a photo- 

 graph of a cut-away model in Fig. 51. Operational and other data are given 



