CROSSTALK BETWEEN COAXIAL CONDUCTORS 



367 



Suppose, for example, that far-end crosstalk measurements are made 

 on two cable sections each of length / with tertiaries terminated as illus- 

 trated in Sketch (a) of Fig. 2. Let the total crosstalk in each section 

 be equal to Fi as defined by equation (5) above. If these two sections 

 are joined together the total crosstalk is 2Fi plus some other terms 

 which represent the interaction crosstalk between the two sections as 

 illustrated in Sketch (b) of Fig. 2. We shall call the component F„„ 



(Xh 



I,e 



•al 



< ? TERTIA RY 

 ^ 



GO- 



l,e-<xl 

 i 



T®, 



TERTIARY < 

 ^ 



T® 



F,= 



lie- 



■al 



(a) 



00^ 



^~I,€-al 



Fnni: 



^ 



Fnn-7^ 

 (c) 



(3> 



CD- 



I,e- 



■2al 



---^ y 



vFnn 



Fff 



k 



T® 



F,_+F^+Fnn + Ff.f- = 



FOR 

 ^^ CALIBRATING^ 



lie 



-2al 



(b) 



lie 



•2al 



■^^^r> 



\Fff 



o 



I|G' 



■2al 



(d) 



J> 





(e) 



Fi + For = 



Fig. 2 — Schematics illustrating far-end crosstalk summation. 



near-end near-end and the component Fff far-end far-end interaction 

 crosstalk. Although inseparable under normal line conditions, these 

 components are definite physical entities and can be isolated as shown 

 schematically on Sketches (c) and (d) of Fig. 2. Thus, both F„„ and 

 Fff can be measured readily. In addition it is possible to measure 

 directly Fi + Fff as shown on Sketch (e). 



This interaction crosstalk between sections is due to crosstalk cur- 

 rents introduced into the outer conductor-sheath tertiary circuit in one 



