*Question T7C10:
Why should the outer jacket of coaxial cable be resistant to ultraviolet light?*  

*Correct Answer is  D: Ultraviolet light can damage the jacket and allow water to enter the cable*  

### AI Response: (may contain errors)  

The correct answer to the question about why the outer jacket of coaxial cable should be resistant to ultraviolet (UV) light is:

**D: Ultraviolet light can damage the jacket and allow water to enter the cable.**

### Explanation of the Correct Answer:
- **UV Damage**: The outer jacket of coaxial cable is typically made from materials like PVC or polyethylene, which can degrade when exposed to UV light. This degradation can lead to cracks and breaks in the jacket.
- **Water Ingress**: If the jacket is damaged, it can allow moisture to enter the cable. Water can cause significant issues, including increased attenuation (signal loss) and potential short circuits.

### Why the Other Choices are Incorrect:
- **A: Ultraviolet resistant jackets prevent harmonic radiation**  
  - This is incorrect because the jacket's resistance to UV light does not directly relate to harmonic radiation. Harmonics are a result of non-linearities in the transmitter or circuit, not the jacket material.

- **B: Ultraviolet light can increase losses in the cable’s jacket**  
  - While UV light can cause physical damage to the jacket, it does not directly increase losses in the cable itself. Losses are more related to the cable's electrical properties and not the jacket's exposure to UV.

- **C: Ultraviolet and RF signals can mix, causing interference**  
  - This statement is misleading. UV light is not an RF signal and does not mix with RF signals. Interference in RF systems is typically due to other RF sources, not UV light.

### Useful Rules of Thumb:
- **Cable Selection**: When selecting coaxial cable for outdoor use, choose cables with UV-resistant jackets to ensure longevity and reliability.
- **Regular Inspection**: Periodically inspect outdoor cables for signs of wear or damage, especially after prolonged exposure to sunlight.

By understanding these points, you can better appreciate the importance of using UV-resistant materials in coaxial cable applications.