VACUUM TUBES AS HIGH-FREQUENCY OSCILLATORS 



105 



spending output of the high-frequency tube is approximately 86 watts 

 with substantially the same plate loss. This strikingly illustrates the 

 improvement obtained by taking into account the factors which 

 become important in the high-frequency range. 



5 80 



40 a: 



z 



35 >3 



z 



UJ 



30 y 

 u. 



25 



60 70 60 90 100 110 120 130 140 150 160 170 180 190 



FREQUENCY IN MEGACYCLES PER SECOND 



Fig. 6 — Output and efficiency as a function of frequency for the tube shown in 

 Fig. 5. A comparison of these curves with those shown in Fig. 1 illustrates the 

 improvement obtained by taking account of those factors which become important 

 at high frequencies. 



Transit Time Becomes More Important 

 In extending the frequency range to 300 megacycles the importance 

 of electron transit time becomes relatively greater. It must be kept 

 as low as possible even at the expense of relatively higher inter- 

 electrode capacitances. In the tube just described for the frequency 

 range around 100 megacycles the reverse procedure is followed; in 



