574 



BELL SYSTEM TECHNICAL JOURNAL 



the like. The sum total of these variations necessitated the maintenance of 

 an average sink margin of 6.7 times in order to insure a minimum of 2.5. 



Figure 72 illustrates further characteristics of the 2K25 oscillator and 

 coupling. These data are the results of standing wave measurements look- 

 ing towards the coupler with the tube inoperative. From such "cold test" 



A?!, 



FREQUENCY 



POWER 



^ 





~i5/ 



'A^C' 



MODE A 

 F = 9350 MC 



Fig. 71. — A Rieke diagram for the 2K25 connected to the load by the coupling of Fig. 

 70. This diagram was obtained for a repeller mode having a drift angle of 15.5 -k radians 

 at a nominal frequency of 9360 mc/s. 



measurements one may determine the intrinsic (Jo of the resonator and the 

 external Qk . The former is a measure of the resonator losses while the 

 latter is a measure of the tightness of coupling of the oscillator to the load. 

 The values of Qo measured from a cold test have little significance in an 

 oscillator in which heating of the resonator and especially of the grids is 

 appreciable. This is particularly true of oscillators tuned by variation of 



II 



