Question T7C10
From subelement T7 - T7C
Why should the outer jacket of coaxial cable be resistant to ultraviolet light?
Why is this correct?
UV light degrades the outer jacket material over time, creating cracks that allow moisture to penetrate the cable. Water intrusion is a major cause of coaxial cable failure and increased loss. Options A and C are incorrect because UV resistance has nothing to do with harmonics or RF interference. Option B is wrong because UV doesn't directly increase jacket losses—it causes physical damage that leads to water entry.
Memory tip
Look for the chain of cause and effect: UV damage → jacket deterioration → water entry → cable failure. This pattern appears in many amateur radio questions about environmental protection and equipment longevity.
Learn more
Outdoor coaxial installations require UV-resistant jackets or physical protection like conduit because prolonged sun exposure breaks down polymers in standard cable jackets. This creates entry points for moisture, which causes impedance changes, increased attenuation, and eventual cable failure. Professional installations often use double-shielded cables with UV-stable outer jackets rated for direct burial or aerial use to maintain transmission line integrity over years of weather exposure.
Think about it
Why do you think amateur radio operators often use electrical tape or heat-shrink tubing to protect outdoor coaxial connections, even when using UV-resistant cable?