CROSSTALK IN COAXIAL CABLES 



355 



The assumption of uniformity of the coaxial Hnes, as regards transfer 

 impedances, and of the tertiary circuits as regards transmission char- 

 acteristics, is a more serious restriction in the computation of near-end 

 crosstalk than in the case of far-end crosstalk. Even for long lengths 

 of cable, the near-end crosstalk is determined almost entirely by the 

 crosstalk behavior of a relatively short length of the cable near the 

 sending end, whereas the average crosstalk characteristics determine 



115 



125 



135 



50 



70 80 90 100 150 200 



FREQUENCY IN KILOCYCLES PER SECOND 



250 



Fig. 2 — Near-end crosstalk for 5-mile length, tertiary short-circuited. 



the far-end crosstalk for a long length of cable. Thus, from measure- 

 ments on representative short lengths, the far-end crosstalk for a long 

 length may generally be computed more accurately than can the near- 

 end crosstalk. 



Similarly, the various types of interaction crosstalk depend largely 

 upon the crosstalk behavior of relatively short lengths of the cable 

 near the junction. In Fig. 3, the far-end far-end interaction crosstalk 

 has been chosen as an illustration of the correlation which has been 

 obtained between. computed interaction crosstalk for the above men- 



