*Question G0A10:
What should be done if evaluation shows that a neighbor might experience more than the allowable limit of RF exposure from the main lobe of a directional antenna?*  

*Correct Answer is  C: Take precautions to ensure that the antenna cannot be pointed in their direction when they are present*  

### AI Response: (may contain errors)  

To address the question regarding RF exposure from a directional antenna, let's break down the correct answer and the reasoning behind it.

### Correct Answer: 
**C: Take precautions to ensure that the antenna cannot be pointed in their direction when they are present.**

#### Explanation:
- **RF Exposure Limits**: The FCC has established limits for RF exposure to protect the public. If an evaluation indicates that a neighbor might exceed these limits, it is crucial to take action to mitigate exposure.
- **Directional Antennas**: These antennas focus energy in a specific direction, which can increase exposure risk if someone is in the main lobe of the antenna's radiation pattern. By ensuring the antenna is not pointed towards the neighbor when they are present, you can effectively reduce their exposure to RF energy.

### Why the Other Choices are Incorrect:
- **A: Change to a non-polarized antenna with higher gain**  
  - **Incorrect**: A non-polarized antenna typically does not exist in the same context as directional antennas. Additionally, increasing gain can actually increase the RF exposure risk, as it focuses more energy in a specific direction.

- **B: Use an antenna with a higher front-to-back ratio**  
  - **Incorrect**: While a higher front-to-back ratio can reduce radiation in the opposite direction, it does not address the issue of exposure to the main lobe. If the neighbor is still in the main lobe, they could still be exposed to excessive RF energy.

- **D: All these choices are correct**  
  - **Incorrect**: Since A and B are not valid solutions to the problem, this choice cannot be correct.

### Useful Formulas or Rules of Thumb:
- **RF Exposure Calculation**: To assess RF exposure, you can use the formula for power density ($S$) at a distance ($d$) from the antenna:
  
  $$S = \frac{P_T \times G}{4\pi d^2}$$

  where:
  - $S$ = power density in watts per square meter (W/m²)
  - $P_T$ = transmitter power in watts
  - $G$ = gain of the antenna (linear)
  - $d$ = distance from the antenna in meters

- **Safety Guidelines**: Always refer to the FCC's guidelines for maximum permissible exposure (MPE) levels to ensure compliance and safety.

By understanding these concepts, you can effectively prepare for the Extra Class exam and ensure safe operation of your amateur radio equipment.