*Question E2E05:
Which of these digital modes does not support keyboard-to-keyboard operation?*  

*Correct Answer is  A: WSPR*  

### AI Response: (may contain errors)  

To understand why WSPR is the correct answer and the others are not, let's break down each digital mode:

1. **WSPR (Weak Signal Propagation Reporter)**:
   - WSPR is designed for weak signal communication and is primarily used for automated reporting of propagation conditions. 
   - It operates in a fully automated mode, meaning it does not support real-time keyboard-to-keyboard communication. 
   - Users cannot interactively send messages back and forth; instead, WSPR transmits short messages that are automatically decoded by receiving stations.

2. **RTTY (Radio Teletype)**:
   - RTTY is a digital mode that allows for keyboard-to-keyboard operation. 
   - It uses frequency shift keying (FSK) to transmit text in real-time, enabling operators to communicate interactively.

3. **PSK31 (Phase Shift Keying, 31 baud)**:
   - PSK31 is another digital mode that supports keyboard-to-keyboard operation. 
   - It is designed for real-time text communication, allowing operators to type messages that are transmitted and received instantly.

4. **MFSK16 (Multi-Frequency Shift Keying, 16 tones)**:
   - MFSK16 also supports keyboard-to-keyboard operation. 
   - It allows for real-time communication and can transmit text and other data interactively.

In summary:
- **Correct Answer: WSPR** does not support keyboard-to-keyboard operation because it is an automated mode focused on propagation reporting.
- **Incorrect Answers: RTTY, PSK31, and MFSK16** all support interactive communication between operators.

No specific formulas are needed for this question, but it's important to remember the characteristics of each mode to differentiate them effectively.