GRID CURRENT MODULATION 



121 



suppressed, it is proportional to the smaller of the two when the ratio of 

 the two inputs is greater than about 3/2. This proceeds from the fact 

 that eq. 5 must be supplemented by many more terms involving 

 higher powers of the impressed potentials, in order to represent the 



6 8 



a. VOLTS 



Fig. 5 



grid current characteristic to any degree of precision when the grid is 

 driven negative. 



The form of the input-output curve is especially valuable for 

 telephony. The relative independence of the larger of the two inputs 

 means that the sideband output will be stable with regard to carrier 

 current variations under the limitations noted. The output approaches 

 a maximum asymptotically, so that the articulation at heavy loads 

 may be expected to hold up better than in those modulating systems in 

 which the output passes through a pronounced maximum. In a 

 system transmitting the carrier, as in radio, and in which a square law 



