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BELL SYSTEM TECHNICAL JOURNAL 



obtain for the modulated output (i.e., terms whose frequencies are of 



the order ^-). 



2tt 



J m =a[-±- + /T* r j,£ cos g/lcos pt. 

 Lr+r p (r+r p y * J 



(12) 



As pointed out above, the first term gives the carrier wave and the 

 second term, the two side bands. It will be remembered that this 



Fig. 38 



equation neglects terms of higher order than the second, which is 

 permissible, so long as the tube characteristic is approximately 

 parabolic. 



Certain points regarding Equation 12 should be noted. In the 

 first place, the amplitude of the side bands is proportional to the 



Fig. 39 



product AB and is therefore, independent of the relative amplitudes 

 of the original carrier and modulating frequencies. Also the modu- 

 lated current is proportional to the first power of B, the amplitude 



