*Question G1A06:
[97.303] Which of the following applies when the FCC rules designate the amateur service as a secondary user on a band?*  

*Correct Answer is  C: Amateur stations must not cause harmful interference to primary users and must accept interference from primary users*  

### AI Response: (may contain errors)  

When the FCC designates the amateur service as a secondary user on a band, it establishes specific rules that amateur operators must follow to ensure that they do not interfere with primary users. 

### Correct Answer: 
**C: Amateur stations must not cause harmful interference to primary users and must accept interference from primary users.**

- **Explanation**: As a secondary user, amateur stations have the responsibility to avoid causing harmful interference to primary users. This means that if a primary user is operating on a frequency, amateur operators must yield to them. Additionally, amateur operators must be prepared to accept interference from primary users, as the primary users have priority on that band.

### Why the Other Choices are Incorrect:

- **A: Amateur stations must record the call sign of the primary service station before operating on a frequency assigned to that station.**
  - **Explanation**: There is no requirement for amateur stations to record the call sign of primary users before operating. The focus is on avoiding interference, not on tracking primary users.

- **B: Amateur stations may use the band only during emergencies.**
  - **Explanation**: This is incorrect because amateur stations can operate on the band under normal conditions, as long as they do not cause harmful interference to primary users. Emergency use is not a restriction placed on secondary users.

- **D: Amateur stations may only operate during specific hours of the day, while primary users are permitted 24-hour use of the band.**
  - **Explanation**: There are no time restrictions placed on amateur operations as secondary users. They can operate at any time, provided they adhere to the interference rules.

### Summary:
- As a secondary user, the key rule is to avoid causing harmful interference to primary users and to accept any interference from them. This ensures that the primary users can operate without disruption, while amateurs can still utilize the band under the established guidelines.