TRANSMISSION OVER SUBMARINE CABLES 



109 



Owing to lack of information concerning the mean radius of the 

 ring of armor wires, two sets of data were computed employing the 

 values c = 0.6148 and c = 0.920, which correspond, respectively, to 

 zero and maximum separation of the armor wires. 



The results of the calculations are shown in Fig. 7. The experi- 

 mental values are indicated by small circles, and agree well with the 

 theoretical values throughout the range of frequencies. The re- 



100 



90 



10 



60 



50 



40 



30 



10 



100 zoo 



300 400 

 Fig. 8 



500 600 



sistance of the sea return increases most rapidly in the region of 

 frequencies used in ordinary telegraphy, to 100 cycles per second. 

 In this range the inductance of the cable also has its greatest values, 

 and these two effects have considerable influence in determining the 

 transmission characteristics of the cable. 



The percentage of the return current that is carried by the armor 

 wires is shown in Fig. 8. 



