ELECTRON TUBES FOR A COAXIAL SYSTEM! 1125 



Assumptions 



I na = 1 



The ratio of the pitch distance to the grid-cathode spacing is held 

 constant. This is done so that the effect of the variation in field along 

 the cathode surface resulting from the finite grid pitch distance will 

 be small and the same throughout the discussion. 



II Ci = 0.0885 X 10' 



■"-(M) 



0.0885 X 10"''^ 



The input and output spaces are treated as if they can be represented 

 by ideal condensers. This amounts to assuming that the grids are per- 

 fect planes and that there are no end effects. The effects of space charge 

 on the capacitances are neglected, and the socket and wiring capaci- 

 tances are also neglected. This means that the resulting calculated 

 figure of merit represents the limiting value inherent in the tube 

 structure. 



/F V^ 



2.33 X lO-'M^ — + Eci) 



III ^fi ~ 7 : ; r73j2 



•■(■-r-f'j 



The expression for plate current assumed is an idealized one, but holds 

 fairly well for these tubes. 



It is assumed that the triode amplification factor is independent of 

 the control-grid voltage. This holds fairly well under the conditions 

 of assumption I. 

 V When the interstage consists of a single parallel tuned circuit, K = 1. 

 This case is assumed. 



Derivations 



Beginning with the above assumptions, and substituting in equation (1), 

 equations (2), (3) and (4) can be derived. The procedure will be outlined 

 below : 



KGrn 



2t(Ci -h C2) 



(1) 



