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BELL SYSTEM TECHNICAL JOURNAL 



effect of the presence of the iron upon the resistance of the return 

 conductor is still noticeable, although it is much less than in the case 

 of the continuous iron sheath. The reason for this is evident after 

 inspection of the curves of Fig. 6, which show the percentage of return 

 current carried by the armor in the two cases. Especially at the 

 lower frequencies, the return current is much more confined by the 

 continuous sheath than it is by the wires. 



As a check of the method, the resistance and inductance of the 

 Seattle-Sitka cable of the United States Signal Corps were calcu- 

 lated for frequencies in the range 50 to 600 cycles per second, and 



Fig. 7 



the values so obtained were then compared with the results of meas- 

 urements recently made upon this cable. ^ The constants used in 

 the calculations were as follows: 



Conductor 



Diameter 216 cm. 



Resistance per nautical mile 9 ohms 



Ruhher Insulation 



Outside diameter 718 cm. 



Capacity per nautical mile Z% mf. 



Armoring 



16 wires each .242 cm. diameter 



Outside Diameter of Cable 2.06 cm. 



' "The Use of Alternating Currents for Submarine Cable Transmission," Frederick 

 E. Pernot, Jour, of the Franklin Instilute, vol. 190, p. 323, 1920. 



