CROSSTALK BETWEEN COAXIAL TRANSMISSION LINES 163 



magnitude of the near-end crosstalk is given by expression (14), which 

 for equal level points becomes 



N\ 



Z\i 



2Zn 



e«Wl - 2g-2«' cos (2,3/) + e"""' 



(60) 



2Va' + ^'' 



Thus, the ratio of the corrected near-end to the far-end crosstalk is 

 obtained by combining equations (60) and (19): 



g"Wl - 2g-^"' cos (2/3/) + g-^"' 



U{a.iy + w 



(61) 



The curve in Fig. 8 gives the db difference between near-end and 

 far-end crosstalk for different frequencies on a 10-mile length of two 



50 100 200 300 500 



FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 8 — Values of 20 logio \FIN\ for a 10 mi. repeater section of two parallel 

 coaxial pairs in continuous contact. Coaxial pairs consist of No. 13 AWG solid 

 copper wire, .267 in. inner diameter copper outer conductor .020 in. thick, and rubber 

 disc insulation. 



parallel coaxial pairs with hard rubber disc insulation. Each pair 

 consists of a copper outer conductor of .267" inner diameter and .020" 

 thick, and a .072" solid copper inner conductor. It is evident that in a 

 single repeater section far-end crosstalk is higher than near-end cross- 

 talk up to about 900 kc. 



When a number of repeater sections are connected in tandem the 

 near-end crosstalk contribution from a single repeater section will reach 

 the terminal of the system modified both in magnitude and in phase due 

 to transmission through intervening sections of crosstalking circuits. 

 At the terminal the phase changes will distribute the crosstalk from all 

 sections in a random manner, which, in accord with both the theory and 



