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BELL SYSTEM TECHNICAL JOURNAL 



Hie first two terms of (38) are the amplification terms and represent 

 undistorted reproduction in the plate circuit of the voltage, e, applied 

 in the grid circuit. The third term of (38) represents the second order 

 effects resulting from the curvature of the characteristics of the 

 vacuum tube. The first part of this term represents the effects of 

 so-called plate curvature detection or modulation, and the second 

 part represents the effects of detection and modulation in the grid 

 circuit. It is with this last-named component that the present paper 

 is most concerned. 



The Grid-Leak Detector 



Fig. 3 shows the usual circuit diagram for a grid-leak detector. 

 It is evident that the impedance, q, in this example is composed of 

 the parallel combination of Rg and C. Suppose that the "/i" and 

 "k" frequencies are both radio frequencies, and that, for them, the 



Fig. 3 — Grid-leak detector 



impedance offered by the resistance and condenser combination is 

 practically that of the condenser, alone. Suppose, further, that 

 practically the only impedance offered by the external circuit to the 

 "{Ji-ky frequency is that of the resistance, Rg, alone. This, of 

 course, assumes that the "h-k" frequency is quite low. Then, when 

 Eb, the voltage of the plate battery, is such that r/ is very small, 

 and when 



e=A cos ht-\-B cos kt 



