SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/ham-coax-moisture

Which of the following causes failure of coaxial cables?

Moisture contamination.

  1. Moisture contamination ✔
  2. Solder flux contamination
  3. Rapid changes in transmitter output power

Why: Water that gets inside coax corrodes the shield and changes the insulation, raising loss and ruining the cable over time.

Huh, didn't know that: Coax jackets should resist ultraviolet light, because sun damage can crack them and let water in.

The dad joke
Why did the coax cable carry an umbrella? It heard moisture was its biggest weakness.
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Sources

  1. NCVEC 2026-2030 Technician Question Pool (Feb 19, 2026 release) https://www.ncvec.org/downloads/2026-2030%20Technician%20Pool%20and%20Syllabus%20Public%20Release%20Feb%2019%202026.pdf

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That's stuff everyone should know.