For the best signal transmission, coaxial cable should be located at least 3 inches away from metal. When cable is touching or very close to metal, the characteristics of the cable are altered. How much the signal is altered depends on the cable's internal shielding, which consists of a braid and/or an additional foil shield. When placed near metal, a cable with 90% braid coverage and no foil shield will be altered less than a cable with 60% braid coverage and no foil shield. All Digital Antenna cable is double shielded, containing a 100% foil shield, high frequency dielectric and copper core.
When placed against metal, a 20 foot, 80% shielded cable (with no foil shielding) may change the efficiency (SWR ratio) of the cable from 1:1.05 to 1:1.2. The system will operate, but not as efficiently as it would with better cable or cable placement away from metal.
Consider all factors of the installation, including proper cable type, cable length and cable placement. Since there is no way to totally eliminate the effects of cable installed next to metal, minimize possible signal degradation by choosing a quality cable with double shielding (100% foil shielding and high braid coverage).
Digital Antenna makes a full line of high quality, low signal loss coaxial cables.