A Negative-Grid Triode Oscillator and Amplifier for Ultra- 

 High Frequencies * 



By A. L. SAMUEL 



^ I ^HE author describes three negative-grid triodes of unusual design 

 A which operate both as oscillators and as amplifiers at ultra-high 

 frequencies. The power output of the smallest tube as an oscillator at 

 1500 megacycles is 2 watts, and is still capable of an output of 1 watt at 

 1700 megacycles with an oscillation limit of 1870 megacycles cor- 

 responding to a wave-length of 16 centimeters. This tube also offers 

 possibilities as an amplifier at frequencies as high as 1000 megacycles. 

 Such capabilities of the negative-grid triode are notable since this de- 

 vice has appeared to lag behind the magnetron as an oscillator at fre- 



Fig. 1 — Experimental double-lead tubes. 



quencies of above roughly 500 megacycles, while the only successful 

 power amplifiers which have been described for frequencies of the order 

 of 300 megacycles are multi-element tubes. 



The triode as used at radio frequencies differs from the multi-element 

 tube chiefly in the manner in which interaction is prevented between 

 the input and output circuits. This is obviously a circuit limitation, as 

 contrasted with the electron transit time limitation which has received 

 so much attention. The greatest opportunity for improvement seems 

 to be in the direction of improved circuit design. The tubes described 

 in this paper were developed from this point of view. 



Sample tubes are shown in Fig. 1 . They differ from previous designs 



* Digest of a paper presented before International Scientific Radio Union April 

 30, 1937 at Washington, D. C. Published in Proc. I. R. E., October, 1937. 



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