THE ELECTRICAL AND MECHANICAL CHARACTERISTICS OF HELICAL MEMBRANE CABLE

Abstract : The construction and electrical characteristics of a range of aluminium-sheathed air-spaced coaxial cables, suitable for operation over a wide range of frequencies, are briefly described. The mechanical characteristics of these cables are then considered and a theory of differential expansion of a coaxial pair is developed. Reference is made to the experimental work undertaken to establish the constants required by the theory and to verify the results given by calculation. It is found that under conditions of no load the cable will meet all the conditions imposed by ambient temperatures ranging from -40C. to +55C. The cable can also be safely operated with power corresponding to the standard rating of the cable applied, but attention is drawn to certain potentially dangerous conditions of installation and operation. Brief reference is made to recent developments in these cables to extend their working range of temperature using new materials, such as polytetrafluorethylene, the linear polyethylenes and irradiated polythene. (Author)