Improving Shielding Effectiveness of Flexible Coaxial Cables

摘要

Early flexible coaxial cables, circa World War II, typically consisted of a bare copper round wire inner conductor, solid or stranded, and a full density extruded polyethylene insulating dielectric making up the core. A copper round wire braid formed the outer conductor. The braid wires could be bare copper or tinned. Silver-plated copper was used for "higher" frequencies. The braiding process consisted of a group of round wires, usually five or six, laid side by side to create a ribbon-like conductor, which in turn was formed into a basket weave to surround the core. This process resulted in an approximately 90 percent coverage of the surface, which was, for the most part, adequate to serve as an outer conductor from an attenuation perspective. Sometimes a second braid was applied over the first braid to obtain better shielding. An extruded polyvinyl chloride jacket completed the cable, providing mechanical protection for the braided outer conductor.