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BELL SYSTEM TECHNICAL JOURNAL 



then tested in the laboratory against the open-wire impedances and found 

 to give fairly high return losses as listed in Table I. The corresponding 

 return losses were also computed and tabulated. The impedances are 

 given for both the network and the theoretical line at typical frequencies 

 over the range from 100 cycles to 20,000 cycles. 



The impedance function for an open-wire line is given by the equation 



^^^) = {m:! 



(1) 



Expanding this function by the binomial theorem and taking the first 

 approximation and further letting G = 0, the impedance function becomes 



Table I 

 104 Mil Cu Open Wire, Dry Weather, 12" Spacing, CS Insulators 



^(X) = 



+ 



1 



1 



Cj {LC)K2/R) X 



(2) 



Applying the method of Brune, this equation yields a network consisting of 

 646.4 ohms in series with a condenser of 1.09 mf. It will also be apparent 

 that eq. (2) has the same form as that of Fig. 1(f), i.e., 



zix) = ft + LI 



and by a 1 to 1 comparison of terms it is evident that 



(3-a) 



and 



Ci = (LC) 



'© 



(3-b) 



