*Question E2D03:
Which of the following digital modes is designed for EME communications?*  

*Correct Answer is  D: Q65*  

### AI Response: (may contain errors)  

The correct answer to the question about which digital mode is designed for EME (Earth-Moon-Earth) communications is **D: Q65**. Here’s why:

### Explanation of the Correct Answer (Q65)
- **Q65** is specifically designed for weak signal communications, making it ideal for EME operations. It uses a highly efficient encoding scheme that allows for the transmission of signals over long distances, such as the path to the Moon and back. This mode is optimized for low signal-to-noise ratios, which is crucial in EME communications where signals can be very weak.

### Explanation of Incorrect Answers
- **A: MSK144**
  - **MSK144** is a digital mode used primarily for meteor scatter communications, not specifically for EME. While it can be used for short-duration contacts, it is not optimized for the long delays and weak signals typical of EME.

- **B: PACTOR III**
  - **PACTOR III** is a digital mode used mainly for point-to-point communications, especially in maritime and remote operations. It is not specifically designed for EME and does not have the same level of efficiency for weak signals as Q65.

- **C: WSPR**
  - **WSPR** (Weak Signal Propagation Reporter) is primarily used for propagation studies and is not designed for two-way communication. While it can be used to detect EME signals, it is not suitable for actual EME contacts due to its one-way nature.

### Summary
- **Q65** is the best choice for EME communications due to its design for weak signals.
- The other modes, while useful in their own contexts, do not meet the specific requirements for effective EME communication.

### Useful Rule of Thumb
When considering digital modes for EME:
- Look for modes that are optimized for weak signals and have robust error correction capabilities. Q65 is a prime example of this.