Deep Dive: T7C10
The correct answer is D: Ultraviolet light can damage the jacket and allow water to enter the cable. The outer jacket of coaxial cable should be resistant to ultraviolet light because UV light can damage the jacket and allow water to enter the cable. UV radiation from sunlight breaks down many plastic materials over time, causing the jacket to crack, become brittle, and eventually fail. Once the jacket fails, water can enter, leading to cable failure. For amateur radio operators, UV-resistant cable is essential for outdoor installations exposed to sunlight. This is especially important for feed lines running outside or on towers.
Why Other Answers Are Wrong
Option A: Incorrect. UV-resistant jackets don't prevent harmonic radiation - harmonics are generated by transmitters, not by cable jackets. UV resistance is for physical protection. Option B: Incorrect. UV light doesn't increase losses in the jacket material itself - it damages the jacket physically, allowing water entry which then causes losses. Option C: Incorrect. UV and RF signals don't mix to cause interference - they're completely different phenomena. UV is light, RF is radio waves.
Exam Tip
UV resistance = prevents jacket damage and water entry. Think 'U'V resistance = 'U'nder 'V'isible protection. UV damages jacket, allowing water entry. Not about harmonics, losses, or interference mixing.
Memory Aid
UV resistance = prevents jacket damage and water entry. Think 'U'V resistance = 'U'nder 'V'isible protection. UV damages jacket, water enters, cable fails. Use UV-resistant cable outdoors.
Real-World Example
Your feed line runs outside along a fence, exposed to direct sunlight. After a few years, the cable jacket becomes brittle and cracks. Water enters through the cracks, causing high losses and cable failure. Using UV-resistant cable would have prevented this - the special jacket material resists UV degradation, maintaining its integrity and keeping water out for many years.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T7C
Reference: 2022-2026 Question Pool · T7 - Practical circuits
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T7C topic.