VACUUM TUBE ELECTRONICS 



71 



tions show that the possibility of securing external circuits having low 

 enough losses to meet the oscillation requirements of most of the 

 diodes which are at present available is not very favorable. The large 

 radio-frequency loss in the filamentary cathodes with which many 

 tubes are supplied is an additional obstacle to be overcome before 

 satisfactory ultra-high-frequency operation of diodes can be expected. 



1.0 



0.9 



Q8 



07 



06 



05 



04 



03 



Q2 



01 







-0.1 



-02 



-03 



-04 



-Q5 



-06 



-0.7 



-OS 



-09 



-1.0 



8 9 10 11 12 13 



I 



Fig. 2 — Electron velocity fluctuation in diodes versus transit angle. 



IV. Triodes with Negative Grid and Positive Plate 



In the application of the fundamental relations to triodes operating 

 with the grid at a negative potential, the problem becomes more com- 

 plicated because of the several current paths which exist within the 

 tube. Moreover, the direct-current potential distribution is disturbed 

 in a radical way by the presence of the negative grid. In fact, the 



