Question T7C09
From subelement T7 - T7C
Which of the following causes failure of coaxial cables?
Why is this correct?
Moisture contamination causes coaxial cable failure by degrading the dielectric material between the center conductor and shield, increasing losses and potentially causing complete failure. Water intrusion creates conductive paths that weren't designed to be there. The other options don't typically cause cable failure: solder flux contamination affects connections but not the cable itself, transmitter power fluctuations affect components but not coax structure, and continuous operation is within normal parameters for properly rated cable.
Memory tip
Look for physical degradation causes in cable failure questions. Moisture is coax's biggest enemy because it attacks the fundamental structure - the insulation between conductors. Environmental factors like water and UV damage are more critical than operational stresses for cable longevity.
Learn more
Moisture contamination creates cascading problems in coaxial systems. It increases dielectric losses, can cause impedance variations leading to higher SWR, and may eventually create complete circuit failure. This is why proper weatherproofing of outdoor connections is essential for reliable amateur radio installations. UV-resistant outer jackets prevent cracking that allows moisture entry, and proper connector sealing prevents water intrusion at connection points.
Think about it
Why do you think moisture affects coaxial cable performance so dramatically compared to other types of electrical cables used in dry indoor applications?