*Question G3C06:
What is a characteristic of HF scatter?*  

*Correct Answer is  B: Signals have a fluttering sound*  

### AI Response: (may contain errors)  

HF scatter refers to a propagation mode where radio signals are reflected off the ionosphere and scatter in various directions. This can lead to unique characteristics in the received signals.

### Correct Answer: B: Signals have a fluttering sound

- **Explanation**: The fluttering sound in HF scatter is due to the rapid changes in the signal path caused by the scattering of signals off irregularities in the ionosphere. This results in variations in the signal strength and phase, leading to a noticeable fluttering effect in the audio output.

### Why the Other Choices are Incorrect:

- **A: Phone signals have high intelligibility**  
  - **Explanation**: While intelligibility can be good in some conditions, HF scatter often results in distortion and fading, which can reduce intelligibility rather than enhance it.

- **C: There are very large, sudden swings in signal strength**  
  - **Explanation**: While signal strength can vary, the characteristic fluttering sound is more indicative of the rapid phase changes rather than large, sudden swings. Sudden swings are more typical of other propagation modes, such as sporadic E.

- **D: Scatter propagation occurs only at night**  
  - **Explanation**: HF scatter can occur at any time of day, although it may be more prevalent during certain conditions. It is not limited to nighttime propagation.

### Summary

HF scatter is characterized by a fluttering sound due to rapid changes in signal characteristics. Understanding these nuances helps in recognizing the behavior of signals under different propagation conditions.