VACUUM TUBE ELECTRONICS 



89 



complete space charge exists in both regions, is, 



r ^ 



V 



Suppose that the grid captured half of the electrons. Then the ratio 

 of transit angles would be 1.41. This would result in a curve lying 

 between A and B in Fig. 11. 



The numbers, w/l, ir, and so forth, which are attached to the curves 

 in Fig. 11 show the values of the grid-plate transit angle, f, which 

 correspond to the points indicated. 



RESISTANCE 

 -0.2 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 



UJ 



^ -0.6 



o 



u -0.8 



Fig. 11 — Ro — Xq diagram for positive grid, slightly positive plate triode with 



cathode space charge. 



Curve A, r) = ^ 

 Curve B,-n = l/2f 

 Curve C, 77 = 1/3^ 



We now come to the problem of obtaining information about the 

 oscillation properties of a tube from a set of curves such as those shown 

 in Fig. 11. In a very loose way, and without proof we may state the 

 results of an extension of Nyquist's ^ rule as follows: 



If an i? — X diagram, which in general may include negative as 

 well as positive frequencies, encircles the origin in a clockwise direc- 



'II. Nyquist, "Regeneration Theory," Bell S\s. Tech. Jour., Vol. 11, p. 126; 

 January (1932). 



