*Question E2E13:
Which of these digital modes has the highest data throughput under clear communication conditions?*  

*Correct Answer is  D: PACTOR IV*  

### AI Response: (may contain errors)  

To determine which digital mode has the highest data throughput under clear communication conditions, we need to consider the data rates of each mode.

### Correct Answer: PACTOR IV

1. **PACTOR IV**:  
   - PACTOR IV is designed for high-speed data transmission and can achieve data rates up to approximately 5,200 bits per second (bps) under optimal conditions. This makes it the fastest among the options provided, especially in clear communication conditions where its full potential can be utilized.

### Why the Other Choices Are Incorrect:

2. **MFSK16**:  
   - MFSK16 is a multi-frequency shift keying mode that typically operates at a data rate of about 316 bps. While it is robust and effective for weak signal conditions, its throughput is significantly lower than PACTOR IV.

3. **170 Hz shift, 45 baud RTTY**:  
   - RTTY (Radio Teletype) with a 170 Hz shift and 45 baud rate has a data throughput of approximately 45 bps. This is much slower compared to the other modes, as RTTY is an older mode primarily used for its simplicity and reliability rather than speed.

4. **FT8**:  
   - FT8 is a mode designed for weak signal conditions and operates at a data rate of about 50 bps. It is highly efficient for making contacts under poor conditions but is not optimized for high data throughput.

### Summary:

- **PACTOR IV** is the correct answer because it offers the highest data throughput among the options, making it ideal for clear communication conditions where speed is a priority.
- The other modes, while useful in different contexts, do not match the data rate capabilities of PACTOR IV.