GB642540A - Improvements in or relating to joints or terminations for high frequency electric cables - Google Patents

Abstract

642,540. Electric resonators. STANDARD TELEPHONES & CABLES, Ltd. March 24, 1947, No. 7990. [Class 40 (viii)] A joint for two lengths of high-frequency cable comprises an odd number of components of such electrical properties and lengths that the vector sum of the reflections at the junctions between the components and between the end components and the cables are substantially zero at any point in the cable at any frequency within the band to be transmitted. A joint for a coaxial cable with solid dielectric, Fig. 1, has three sections of differing dielectric properties. The central section comprises a disc 8 secured to a copper rod 7 soldered within the ends of the inner conductors 5 and forming a water-tight barrier between the sections of cable. The dielectric is removed from a section of cable on each side of the barrier for such a distance that the vector sum of the reflections is zero. A termination for a balanced pair cable, Fig. 2 (not shown), to be connected to equipment of the same impedance as the cable, comprises two sections forming water-tight barriers separated by a section without dielectric of such length that the total reflections are zero. A joint between coaxial cables with dielectric spacers in the form of cylinders closed at one end, Fig. 5, has five sections. The central section 39 forms a water-tight barrier and a section without dielectric on either side is followed by a section formed by an incomplete spacer 41, 42. In a modification, Fig. 6 (not shown), the incomplete spacers on either side of the joint are closed by discs of similar material to that of the central barrier disc. The joint has seven components, the central barrier disc and, on either side, an air-spaced section, a disc and a section formed by that portion of the incomplete spacer over half a spacer in length. The Specification gives numerical examples for calculating the required lengths of the air-spaced sections in the joints.