746 



BELL SYSTEM TECHNICAL JOURNAL 



Values of the attenuation constant of open-wire pairs of different 

 gages when equipped with DP insulators are presented in Figs. 9 and 

 10. The values are plotted in db per mile.^" 



The attenuation values of Figs. 9 and 10 have been determined for 

 a temperature of 20 deg. cent. (68 deg. fahr.) and for the dry and wet 



.300 



.250 



_i 



i 



a. 



UJ 

 Q. 



(B 

 Q 



z 

 o 



I- 

 < 



Z 



.200 



.150 



.100 



.050 



10 20 30 



FREQUENCY-KILOCYCLES 



40 



50 



Fig. 10 — Carrier frequency attenuation of open-wire pairs equipped with DP 



insulators. 



weather values of leakage conductance previously presented. It will 

 be recalled that these values of leakage are derived on the basis of 40 

 pairs of insulators per mile, and are intended to represent, not average 

 values, but the highest values ordinarily obtained under conditions of 

 dry and wet weather. Systems are ordinarily engineered on the basis 

 of the extreme wet weather attenuation values. When a line runs 

 through the more arid parts of the country, however, advantage is 



i^See "Decibel— The N'ame for the Transmission Unit," by \V. H. Martin, 

 Bell System Tech. Jl., January 1929, pp. 1-2. 



i 



