NEGATIVE-GRID TRIODE OSCILLATOR AND AMPLIFIER 571 



remaining is that caused by one filament lead and that this lead is 

 extremely short. 



In the present investigation the method of neutralizing admittance 

 coupling has been that disclosed by H. W. Nichols in U. S. Patent 



200 



250 



300 350 400 450 500 550 

 FREQUENCY IN MEGACYCLES PER SECOND 



Fig. 4 — Comparison plot of output efficiency for the large tube when operated^single- 

 ended and double-ended. 



20 



200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 

 FREQUENCY IN MEGACYCLES PER SECOND 



Fig. 5 — Output and efficiency as a function of frequency for the large tube. 



1,325,879 and involves the resonating of the offending admittances at 

 the desired operating frequency so that the resulting parallel admit- 

 tance is reduced to a very low value. This takes the form of an in- 

 ductance connected between the grid and plate of the tube and adjusted 



