Abstract: A coaxial cable [10, 50] includes an inner conductor [11] that is separated from an outer conductor [13] by a layer of insulating material [12]. The outer conductor includes a thin sheet of metallic foil that envelops the insulating material and has a seam [14] that extends in the longitudinal direction of the cable. In a first embodiment, the insulated conductor is axially rotated (twisted) with respect to its own longitudinal axis. In a second embodiment, the outer conductor is wrapped around the layer of insulating material. In both embodiments, there is relative rotation between the insulated conductor and the outer conductor. This practice is referred to as relative insulated conductor rotation, and it significantly improves the structural return loss characteristics of a coaxial cable when the outer conductor includes an asymmetry, such as a seam, that extends in the longitudinal direction of the cable.

Abstract: During the manufacture and/or packaging of insulated conductors, insulation defects are detected, measured, and classified by the methods and apparatus of this invention. As a twisted pair of insulated conductors (21-21), for example, is advanced along a manufacturing line (25), the insulation covers (23-23) are engaged by a probe (32) which is connected to a source of electrical power and to an electrical circuit (30). The circuit is adapted to process signals received from the probe and to make comparisons with stored signals to indicate the occurrence of pinholes, faults or bare wire in the insulation covers. In order to be accurate in its comparison and classification, the circuit includes provisions for correcting for current flow between the probe and the metallic conductors prior to and subsequent to the pair being moved through the probe and for the thickness of the probe.