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BELL SYSTEM TECHNICAL JOURNAL 



As pointed out earlier, if the first guess is not a sufficiently good approxi- 

 mation a second try can be made based on the evident shortcomings of the 

 first try. In this case if a closer approximation is required up to 20 kc the 

 next step might be to change Cz to .8 mf which would make the Zz contribu- 

 tions above .1 kc somewhat less negative and would therefore raise the net- 

 work locus. Then changing Ri to 140 ohms would shift the locus 10 ohms 

 to the right. The resulting locus would be somewhat closer at the upper 

 frequencies but the change would not be necessary unless a rather high 

 degree of balance is required. 



Table Ill-b 

 19 Ga. Quadded Non-Loaded Toll Cable 



In general the success of a trial of the graphical construction may be 

 determined immediate^ by comparing about three frequencies of the line 

 and network. 



Table Illb gives the computed network impedance and the line imped- 

 ance. The computed return loss is also given and equals or exceeds 25 db 

 at all frequencies above 200 cycles. 



It is apparent that the resistance and condenser elements of the generat- 

 ing functions are in descending order of magnitude with increasing fre- 

 quency for the non-loaded cable the impedance locus of which is essentially 

 a straight 45° line. As pointed out earlier, the series addition of such gener- 

 ating functions may be converted to a ladder structure^, whose sections will 

 have a tapered characteristic rather than repetitive. 



^ .\ppendix D of Transmission Circuits by K. S. Johnson. 



