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THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1957 



production line in the American factory, no other electrical measure- 

 ments could be made on the components of the cable until it was com- 

 pletely armored. In the British factory, tests for information purposes 

 only were made on the cable in the coaxial stage. These tests included 

 measurements of attenuation, internal impedance irregularities, and 

 terminal impedances. They served as a means of evaluating the changes 

 in the electrical performance during armoring. 



The insulation resistance requirement after armoring and storage 

 under water for at least 24 hours was 100,000 megohm-miles. The cable 

 had to withstand 50,000 volts for a period of one minute without failure. 



ATTENUATION MEASUREMENTS 



As an aid in achieving the desired uniformity of product, new meas- 

 uring equipment of improved accuracy was provided. A block schematic 

 of this equipment is shown in Fig. 10. The requirements for this equip- 

 ment were that it should be capable of measuring a 37 to 44 mile section 

 of cable with an absolute accuracy of 0.04 db and a precision of 0.01 db 

 in the frequency range from 1 to 250 kc. 



The attenuation of the cable was measured at 10 kc intervals from 

 10 kc to 210 kc and measured values were corrected to 37°F, using the 

 changes in attenuation owing to temperature, shown in Fig. 11. By 

 comparing the corrected values with the design characteristic shown in 

 Fig. 12, the deviations were determined. Both the attenuation charac- 



20 



40 60 80 100 120 140 



FREQUENCY IN KILOCYCLES PER SECOND 



160 



180 



Fig. 11 • — Change in cable attentuation due to temperature as a function of 

 frequency. 



