*Question G4E01:
What is the purpose of a capacitance hat on a mobile antenna?*  

*Correct Answer is  C: To electrically lengthen a physically short antenna*  

### AI Response: (may contain errors)  

A capacitance hat is used on a mobile antenna to electrically lengthen a physically short antenna. Here's why:

1. **Correct Answer (C): To electrically lengthen a physically short antenna**
   - A capacitance hat adds capacitive reactance at the top of the antenna, which effectively increases the electrical length of the antenna without increasing its physical length. This helps the antenna resonate at a lower frequency than it would otherwise.

2. **Why the other choices are incorrect:**
   - **Choice A: To increase the power handling capacity of a whip antenna**
     - A capacitance hat does not affect the power handling capacity. Power handling is more related to the materials and construction of the antenna.
   - **Choice B: To reduce radiation resistance**
     - Radiation resistance is a function of the antenna's design and its environment, not directly affected by a capacitance hat. The hat primarily affects the electrical length.
   - **Choice D: To lower the radiation angle**
     - The radiation angle is influenced by the height and design of the antenna, not by the presence of a capacitance hat. The hat's main role is to adjust the electrical length.

In summary, the capacitance hat is a practical solution for making a short antenna resonate at the desired frequency by increasing its electrical length.