VACUUM TUBES AS HIGH-FREQUENCY OSCILLATORS 107 



somewhat beyond 400 megacycles as contrasted with 230 megacycles 

 for the other tube. This is due, primarily, to the material decrease in 

 lead inductance. The decreased losses resulting from the minimized 

 transit time more than compensate for the increased circuit loss 

 resulting from the required higher charging currents to the inter- 

 electrode capacitances. Its mutual conductance of 2200 micro- 



120 



no 



100 

 90 



80 



in 



(- 



5 70 



- 60 



I- 



^ 50 



:d 

 o 



40 

 30 

 20 



150 175 200 225 250 275 300 325 

 FREQUENCY IN MEGACYCLES PER SECOND 



350 375 400 



Fig. 8 — Output and efficiency curves for 2 tubes of the type shown in Fig. 7. 



ohms and the sharp cut-off shown by the static characteristics indicate 

 that those electrical characteristics which are important for efficient 

 oscillators in the low-frequency range have not been sacrificed in 

 meeting the requirements of 300-megacycle operation. 



Output and efficiency curves for this tube are shown in Fig. 8. 



