*Question E2E06:
What is the length of an FT8 transmission cycle?*  

*Correct Answer is  C: 15 seconds*  

### AI Response: (may contain errors)  

The length of an FT8 transmission cycle is a key aspect of understanding this digital mode used in amateur radio.

1. **Correct Answer Explanation**:  
   The correct answer is **15 seconds**. FT8 operates with a fixed transmission cycle of 15 seconds. This cycle includes both the transmission and reception of data, allowing for efficient communication even under poor conditions. Each FT8 transmission consists of a series of 15-second intervals where the station alternates between transmitting and receiving.

2. **Incorrect Choices Explanation**:  
   - **A: It varies with the amount of data**: This is incorrect because FT8 has a standardized cycle time of 15 seconds, regardless of the amount of data being sent. The protocol is designed to fit within this fixed time frame.
   - **B: 8 seconds**: This is incorrect as FT8 does not operate on an 8-second cycle. Other digital modes may have different timing, but FT8 specifically uses 15 seconds.
   - **D: 30 seconds**: This is also incorrect. While some modes may have longer cycles, FT8 is specifically designed for a 15-second cycle to maximize efficiency in weak signal conditions.

3. **Useful Rules of Thumb**:  
   - FT8 is designed for weak signal communication, making it popular for low-power operations.
   - The 15-second cycle allows for quick exchanges, making it suitable for contesting and casual contacts alike.

Understanding the fixed nature of the FT8 transmission cycle is crucial for effective operation and for answering related exam questions.