*Question G8C07:
Which of the following narrow-band digital modes can receive signals with very low signal-to-noise ratios?*  

*Correct Answer is  B: FT8*  

### AI Response: (may contain errors)  

To understand why FT8 is the correct answer for receiving signals with very low signal-to-noise ratios, let's break down each option:

### Correct Answer: FT8
- **FT8** is designed specifically for weak signal communication. It uses a very robust error correction scheme and operates with a time-synchronized protocol, allowing it to decode signals even when the signal-to-noise ratio (SNR) is as low as -20 dB. This makes it highly effective for weak signals, especially in challenging conditions.

### Why the Other Choices are Incorrect:
- **A: MSK144**
  - **MSK144** is a mode used primarily for meteor scatter communications. While it can handle some noise, it is not as optimized for very low SNR as FT8. It typically requires a better SNR to decode signals effectively.

- **C: AMTOR**
  - **AMTOR** (Automatic Mail Transmission Over Radio) is an older mode that combines error correction with a more traditional approach to digital communication. It is not as resilient to low SNR conditions compared to FT8, making it less effective for weak signals.

- **D: MFSK32**
  - **MFSK32** (Multi-Frequency Shift Keying) is a digital mode that can handle moderate noise levels but does not perform as well as FT8 in very low SNR situations. It typically requires a clearer signal for reliable decoding.

### Summary
- FT8 is specifically engineered for low SNR environments, making it the best choice among the options provided. The other modes, while capable, do not match FT8's performance in weak signal conditions.

### Useful Rule of Thumb
- When dealing with digital modes, remember that modes designed for weak signal communication (like FT8) often utilize advanced error correction and synchronization techniques, allowing them to perform better in noisy environments.