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BELL SYSTEM TECHNICAL JOURNAL 



identity of the curves for these components in the two figures shows 

 that the degree of modulation has practically no effect on the relative 

 importance of the interference which occurs when the same programs 

 are transmitted. 



If we again assume that the total interference may be represented by 

 a fictitious component of twice the amplitude of the q -\- u component, 



Fig. 6 — Relative amplitudes of undesired frequencies as a function of the ratio of 

 the amplitudes of the desired and the interfering carriers. Attenuation constant 

 a twice that of Fig. 5. 



we may take our data from the dash-dot line of Fig. 4. This should 

 represent the case fairly well for the straight line detector but when a 

 square law detector is used, greater interference should result due to the 

 importance of the p ± u terms. However, we shall consider only the 

 q zL u group and the phenomena associated with the square law case 

 may be readily inferred. In order that the displaced side band 

 interference may be 40 db down from the desired speech the carrier 

 ratio must have a value of 0.01, while if it is to be 20 db down, this 

 value must be 0.1. The first value corresponds to curves 5 of Figs. 



