11-1 



THE MAGNETRON 



583 



For the other modes, the phase shift 

 between adjacent segments of the 

 anode is some value other than 180°, 

 the fields in the different resonators 

 will not be uniformly strong, and less 

 efficient operation is observed. 



The undesired modes are most 

 troublesome when their frequencies 

 are close to the desired ir mode. To 

 increase the frequency separation 

 between modes, strapping of the 

 anode is frequently resorted to. 

 Strapping may take a variety of 

 forms. One typical form, double ring 

 strapping, is shown schematical 

 Fig. 11-5. The effect of strapping 

 upon increasing the separation of the 

 resonant frequencies of the various 

 modes is shown in Fig. 11-6. 



Another type of anode block that is widely used is the rising-sun anode 

 shown in Fig. 11-7. In this system, the alternate, cavities are of unequal 



Fig. 



11-5 Double-Ring Strapping on a 

 ■ Magnetron Anode Block. 



DEGREE OF STRAPPING 



Fig. 11-6 Effect of Strapping upon 



Mode Separation for an Eight-Resonator 



System. 



Fig. 11-7 



Rising-Sun Resonant System 

 for Magnetron. 



dimensions. This results in a wider separation of modes than is found with 

 an unstrapped system of equal resonators, and it is not necessary to strap 

 a rising-sun anode. There is one important difference between the mode 

 spectrum of a strapped system and a rising-sun system. With the strapped 

 system, the desired -k mode is the lowest frequency mode, while for the 

 rising-sun system, the desired tf mode lies between groups of modes at higher 

 and lower frequencies. 



