*Question T7C11:
What is a disadvantage of air core coaxial cable when compared to foam or solid dielectric types?*  

*Correct Answer is  C: It requires special techniques to prevent moisture in the cable*  

### AI Response: (may contain errors)  

Air core coaxial cable has specific characteristics that differentiate it from foam or solid dielectric types. 

### Correct Answer: C
**It requires special techniques to prevent moisture in the cable.**

- **Explanation**: Air core coaxial cables are more susceptible to moisture ingress because they lack a solid or foam dielectric that can provide a barrier. Moisture can lead to increased loss and degradation of the signal quality. Therefore, special sealing techniques or protective measures are necessary to ensure the cable remains dry and performs optimally.

### Why the Other Choices are Incorrect:

- **A: It has more loss per foot**  
  - **Explanation**: Air core coaxial cables typically have lower loss compared to foam or solid dielectric cables at higher frequencies. The absence of a dielectric material reduces dielectric losses, making air core cables more efficient in terms of signal transmission.

- **B: It cannot be used for VHF or UHF antennas**  
  - **Explanation**: This statement is false. Air core coaxial cables can be used for VHF and UHF antennas. In fact, they are often preferred in certain applications due to their lower loss characteristics.

- **D: It cannot be used at below freezing temperatures**  
  - **Explanation**: Air core coaxial cables can be used at low temperatures. The performance of the cable is not significantly affected by cold weather, unlike some foam or solid dielectrics that may become brittle or lose performance in extreme cold.

### Summary
- Air core coaxial cables require special techniques to prevent moisture ingress, making option C the correct answer. 
- The other options are incorrect as they misrepresent the capabilities and performance characteristics of air core coaxial cables. 

This understanding is crucial for selecting the right type of coaxial cable for your amateur radio applications.