Preliminary Study of a Miniature Underwater Cable System

Certain aspects of feasibility of a miniature submarine cable-transmission system have been studied. The system is small and light, and designed for use in military applications as an expendable item where submarine cables of conventional design would be uneconomical. It weighs about 125 pounds per mile, transmits 1.35 million pulses per second of a pulse-code modulated (PCM) signal, and is powered by 4.5 ma with a voltage drop of about 2 volts per mile. Several armorless cables were tested. All have a steel core with a layer of copper for the center conductor, and extruded polyethylene dielectric. They differ in the way in which the center conductor is fabricated, in the materials of the outer conductor, and in the way in which it is held in place over the dielectric. The transistor repeater uses one transistor and eight passive components. It has a 17-db gain and an output of 0.8 volts into a 75-ohm line. The repeater housings are hollow cylinders of beryllium copper, 2 1/8 inches by 7/16 inches. The insulation of the transmission line is joined to the ends of the housing by an adhesive and by a mechanical seal. The cable tension is transferred to the housings by hollow ceramic insulating cones. The housings were tested in 13,200 psi hydrostatic pressure and to 120 pounds axial tension. A system of five repeaters in 18,000 feet of line was laid in Sandy Hook Bay and was operable for thirteen months.