CROSSTALK BETWEEN COAXIAL CONDUCTORS 

 whence, for both components, 



371 



iVs + iV4 = Ni 



2Z 



+ 



J_ 



AZu 74^ — 7^ 



27 



1 



7r 



4Z44 74^ 



1 - 2e-(^^+>>^ + e-"^' 

 274 



(20) 



In a section where the tertiary circuit is electrically long equation (20) 

 reduces to 



Ni = 



7 n2 



2Z 



1 



1 



74" 



4Z44 74^ — 7^ 



1 - e-2^' 



27 



1 



74' 



' 4Z44 74^ 



and when / is electrically short it reduces to 



74 



1 + e-^y^ 



274 



Ni 



^Z^\ ±__ 

 2Z iZzz 



4Z44 2 



(21) 



(22) 



which is the same as for far-end crosstalk in very short lengths as given 

 in equation (7). 



As pointed out earlier the expression for near-end crosstalk even 

 when the tertiary circuit is electrically long is more complicated in form 

 than for far-end crosstalk because of the terms 1 — e-^f' and 1 + e"^''''. 

 This may be seen by comparing formulas (6) and (21). 



Nevertheless it is possible to see from (21) that the presence of the 

 tertiary circuit acts to reduce near-end crosstalk as it did in the case of 

 far-end crosstalk. The first term of (21) is less than the near-end 

 crosstalk without the sheath (equation (18)) by the factor 



1 



1 



74-= 



4Z44 74^ — 7 



Z33 



2 7 



= 1 - ^ 



74^= 



4Z44 74^ - 7 



This is the same factor by which far-end crosstalk is reduced in very 

 long lengths as brought out in the discussion of equation (6). How- 

 ever, the second term in equation (21) prevents this complete reduction 

 from ever taking place in the case of near-end crosstalk. 



PART II— EXPERIMENTAL RESULTS 



The crosstalk measurements presented here were made on and 

 between sections of twin coaxial cable of various lengths from 73 feet 



