COMMON FREQUENCY BROADCASTING 



595 



of modulation. It will be seen from these curves that making the 

 modulation of the two carriers equal effects a tremendous reduction in 

 the amount of distortion present in the hollows of the fading cycle that 

 occur when the carriers approach phase opposition, i.e., 7 = 180 de- 

 grees. Also it will be seen from a comparison of the family of curves 

 for 100 per cent and 50 per cent modulation (J/o = 1 and Mi = 0.5), 



60 90 120 150 180 



r RADIO PHASE ANGLE IN DEGREES 



Fig. 12— Ratio of distortion products to fundamental for the point directly be- 

 tween and equidistant from the two stations, with varying carrier phase angle, 7, 

 and different degrees of modulation of the two carriers, (V = M1/M2), where the 

 audio phase angle /3 = and the field strength ratio E1/E2 = 1. 



that a reduction in the degree of modulation of both carriers by 6-db 

 effects an equal reduction in the amount of distortion. Furthermore, 

 a comparison of the curves in the successive figures will show how 

 rapidly the maximum distortion due to the unequal degrees of modula- 

 tion of the two carriers is reduced as the field strength ratios diverge 

 from unity. 



In the second series of curves. Figs. 15, 16, and 17, the effect of 

 varying the carrier phase angle is shown for different representative 



