314 



BELL SYSTEM TECHNICAL JOURNAL 



The shapes of attenuation-frequency curves at high, low and intermediate 

 temperatures are shown by the curves of Fig. 14. These curves do not 

 appear to be strikingly different in shape but more detailed study of the 

 variations with temperature show the rate of change (decibels per degree per 

 mile) to vary with frequency according to the curve of Fig. 15. The fre- 

 quency of maximum rate of variation depends upon the gauge, as does the 



5.0 



y 2.fe 



10 20 30 40 50 60 70 80 90 100 



FREQUENCY- KILOCYCLES 



Fig. 14 — Attenuation; decibels per mile — 19 gauge pairs 



actual rate of change. If the curves are plotted as attenuation coefficients 

 (db per db per degree, Fahrenheit) with the abscissa 



B = 



y Rao 



frequency 



per 1000 ft ' 



the same as for skin and proximity effects in Fig. 2, the peaks are brought 

 together as indicated in Fig. 16. 



