*Question E2E07:
How does Q65 differ from JT65?*  

*Correct Answer is  C: Multiple receive cycles are averaged*  

### AI Response: (may contain errors)  

Q65 and JT65 are both digital modes used in amateur radio for weak signal communication, but they have some differences in their operation and features.

### Correct Answer: C: Multiple receive cycles are averaged

1. **Why the correct answer is correct:**
   - **Multiple receive cycles are averaged:** Q65 is designed to improve the decoding of weak signals by averaging multiple receive cycles. This means that it can combine information from several transmissions to improve the likelihood of a successful decode, which is particularly useful in very weak signal conditions.

2. **Why the other choices are incorrect:**
   - **A: Keyboard-to-keyboard operation is supported:** Neither Q65 nor JT65 is designed for real-time keyboard-to-keyboard communication. They are both structured around pre-defined message formats and are not suitable for conversational exchanges.
   - **B: Quadrature modulation is used:** Both Q65 and JT65 use different modulation schemes, but quadrature modulation is not a distinguishing feature between them. JT65 uses a form of MFSK (Multiple Frequency-Shift Keying), while Q65 uses a more advanced modulation technique, but quadrature modulation is not specifically highlighted as a difference.
   - **D: All these choices are correct:** Since A and B are incorrect, this choice is also incorrect.

### Additional Notes:
- **JT65** is known for its ability to decode signals that are below the noise floor, making it popular for moonbounce (EME) and other weak-signal work.
- **Q65** builds on the strengths of JT65 by incorporating techniques like averaging multiple receive cycles, which enhances its performance in challenging conditions.

Understanding these differences can help you choose the right mode for your communication needs, especially in weak signal environments.