ULTRA-HIGH-FREQUENCY POWER AMPLIFIER 



19 



pletely inoperative. The variation in the input resistance with the 

 operating conditions of the tube for a constant frequency of 150 

 megacycles is shown in Fig. 9. It is evident that if a high value of input 

 resistance is to be realized, high anode potentials with low space cur- 



a^o 



30 



20 



10 



300 400 500 600 

 PLATE POTENTIAL IN VOLTS 



90(7 



Fig. 7 — Anode characteristics of the double pentode tube. 



rents must be used. The reduction in the filament grid spacing made 

 possible by the unusual construction is in a large measure responsible 

 for the improvement in the input resistance just noted. 



A characteristic measurable only at the operating frequency is the 

 interaction between the input and output circuits which results from 



