SF System: Ocean Cable and Couplings

This article covers the design of the cable and of the coupling used to join the cable to the repeater or equalizer. Other articles in this issue give the details of the SF System, repeater, and power circuitry. To provide 800 two-way, 3-kHz voice-frequency message channels, frequencies in the range from 500 kHz to 6 MHz are used. The cable design must provide a transmission medium in this frequency range whose loss, stability and uniformity allow the repeatered system to meet modulation and noise requirements for a span of 4000 nautical miles. If SD Cables were used for the broader band SF System, its 6 MHz loss at 10°C. and zero pressure would amount to 24,000 dB (6.0 dB/nm). To compensate for this loss, the large number of repeaters required would degrade the modulation performance and increase both the overall system cost and the possibility of failure. Higher voltage would also be needed. To minimize the number of repeaters required for the desired increased channel capacity and to optimize system cost, a lower loss cable is dictated. 699