These cables are of coaxial cables, with outer conductor made of alum tubes and inner conductor made of copper-covered alum, suitable for use in CATV trunk engineering projects. Both outer/and inner conductor materials have the same expansion coefficients and elastic modules. This will greatly cut down the failures caused by pulling/bending of the inner conductor. Compared with cables with alum strips or woven thread plus alum foils, the SYWLY-75 serial cables have such advantages as better screening ability, smaller attenuation, and better echo wave loss performance, etc. With product parameters up to the international standards for similar products overseas.