Antennas System Cables and Guys Combining High Strength and Optimum Dielectric Characteristics

A comparison has been made of high strength filament materials having low dielectric and loss-tangent properties for use in antennae cables; lines and guys. The availability of type S glass fibers of higher strength than type E and the more recent production of high-modulus carbon filaments, and high-modulus organic type polymeric fibers offer several materials to choose from for optimum design. Since frequently both the mechanical and electrical properties are important for cables, a brief review is given of properties considered for final design and production. A specific problem and solution is analyzed with supporting data. At the Cornell University National Astronomy and Ionosphere Center in Puerto Rico, cables used in the antennas ,system had to meet the following unique combination of requirements: 1) high modulus for a low total elongation, 2) assurance of rigidity at comparatively low prestrain loads, and 3) low loss-tangent and dielectric properties. The final lines involved use of a recently developed PRD-49 organic fiber exhibiting higher polymer strength and modulus than previously obtainable. A modulus of 16.5x10
⁶
psi was obtained for a line capable of supporting a 19, 000 Ib load and weighing approximately 0.04 Ib/ft of length. The implications of this work in other antennae and related design problems are also discussed.