*Question E0A10:
When must an RF exposure evaluation be performed on an amateur station operating on 80 meters?*  

*Correct Answer is  A: An evaluation must always be performed*  

### AI Response: (may contain errors)  

To understand when an RF exposure evaluation is required, it's important to know the FCC rules regarding RF safety for amateur radio operators.

### Explanation:

1. **Correct Answer: An evaluation must always be performed**

   - The FCC requires that all amateur radio stations perform an RF exposure evaluation to ensure compliance with safety guidelines, regardless of the frequency band or power level. This is to ensure that the station does not expose people to RF levels that exceed the Maximum Permissible Exposure (MPE) limits.

2. **Why the other choices are incorrect:**

   - **Choice B: When the ERP of the station is less than 10 watts**
     - This is incorrect because the requirement to perform an RF exposure evaluation is not solely based on the ERP being above or below a certain threshold. Evaluations are required for all stations to ensure compliance with safety standards.

   - **Choice C: When the station’s operating mode is CW**
     - This is incorrect because the requirement to perform an RF exposure evaluation is not dependent on the operating mode. All modes, including CW, require an evaluation to ensure safety.

   - **Choice D: When the output power from the transmitter is less than 100 watts**
     - This is incorrect because the need for an RF exposure evaluation is not determined by the transmitter's output power alone. Evaluations are necessary for all power levels to ensure compliance with MPE limits.

### Useful Information:

- **Maximum Permissible Exposure (MPE):** The FCC has established MPE limits for different frequencies and exposure conditions. These limits are designed to protect humans from harmful levels of RF radiation.
  
- **RF Exposure Evaluation:** This involves calculating the potential RF exposure levels in areas accessible to people and comparing them to the MPE limits. Factors such as frequency, power level, antenna gain, and distance from the antenna are considered.

By understanding these requirements, amateur radio operators can ensure their stations are safe and compliant with FCC regulations.