REFLEX OSCILLATORS 



575 



the capacitance of the interaction gap. It is possible to make hot tests 

 in which the thermal conditions cf operation are estabhshed without the 

 interaction effects of the beam, but these measurements are not available 

 for the 2K25. The external Qb is not affected, at least to a iirst order, by 

 thermal effects in the resonator. The third curve of Fig. 72 shows the ratio 

 of the power delivered when a matched load is coupled to the coupler to the 

 power delivered to a load which presents optimum impedance to the oscil- 



-►^ 600 D 



8800 9000 9200 9400 

 FREQUENCY IN MEGACYCLES PER SECOND 



Fig. 72. — Variation of the percentage of maximum power output delivered, unloaded 

 Q, Qo , and external (J, Qe . as functions of frequency for the 2K25 when coupled to the 

 characteristic admittance of the 1" x \" guide with the coupling of Fig. 70. The power 

 variation is for a mode having 15.5 -k radians drift. 



lator. These data are given for the normal operating repeller mode as dis- 

 cussed below. 



It was pointed out early in this work that the available power output and 

 electronic tuning have a contrary variation with respect to the number of 

 cycles of drift in the repeller space. Consequently, this is one of the most 

 important and exasperating parameters of the tube. Fig. 73 is a diagram 

 illustrating the characteristics of a typical W.E. 2K25 oscillator. The 

 abscissa is the repeller-cathode voltage which, for a fixed resonator voltage, 

 determines the drift angle. Thus, as this voltage is made increasingly 

 negative, successive modes of oscillation appear, corresponding to consecu- 



