270 



BELL SYSTEM TECHNICAL JOURNAL 



This expression is the locus of values of the ratio p which give 

 minimum attenuation for different assumed values of the ratio a. 

 The unique values of hjc = a and cjb = p, which give minimum 

 attenuation for a given value of m/V« and Li, may be obtained by 

 taking pairs of a and p which satisfy equation (50), substituting them 

 in equation (45), and graphically determining the pair for which the 

 attenuation is a minimum. 



Figures 1 1 and 12 show a graph, obtained in this way, of the optimum 



a tr a: 

 ^ -1 o 



o y (J 

 P I li. 

 < in o 



"'^'^ 

 5 o uj 



8 



7 

 6 

 5 

 4 



0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 I.I 1.2 



RATIO OF HIGH-FREQUENCY RESISTANCES (STRANDED INNER CONDUCTOR TO 

 SOLID CONDUCTOR OF SAME SIZE BUT OF MATERIAL OF OUTER CONDUCTOR, -^=A 



VTT' 



Fig. 11 — Optimum diameter ratio of shielded stranded pair. 



0.1 0.2 0.3 04 0.5 0.6 0.7 0.8 0.9 1.0 I.I 



RATIO OF HIGH-FREQUENCY RESISTANCES (STRANDED INNER CONDUCTOR TO 

 SOLID CONDUCTOR OF SAME SIZE BUT OF MATERIAL OF OUTER CONDUCTOR, 



Fig. 12^0ptimum spacing ratio of shielded stranded pair. 



Vn-' 



proportions for a shielded stranded pair, plotted as a function of >?;/V« 

 for a value of Li equal to 0.5 abhenry per centimeter, which corre- 

 sponds to the case where each conductor is completely stranded. 



Fair with Shield Return 

 The discussion of the shielded pair thus far has been concerned 

 solely with the circuit which employs one of the enclosed conductors 

 as a return for the other. A second circuit may be obtained by 



