*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 is a mode of propagation that occurs when radio waves are scattered by irregularities in the ionosphere. Here's why the correct answer is correct and why the other choices are incorrect:

1. **Correct Answer: Signals have a fluttering sound**
   - HF scatter signals often have a characteristic fluttering or wavering sound. This is due to the multiple paths the signal takes as it is scattered by the ionosphere, causing rapid changes in phase and amplitude.

2. **Why the other choices are incorrect:**
   - **A: Phone signals have high intelligibility**
     - This is incorrect because the fluttering and multipath nature of HF scatter can actually reduce intelligibility, making it harder to understand voice communications.
   - **C: There are very large, sudden swings in signal strength**
     - While HF scatter can cause some variation in signal strength, it is typically not characterized by very large, sudden swings. Instead, the changes are more subtle and continuous.
   - **D: Scatter propagation occurs only at night**
     - This is incorrect because HF scatter can occur at any time of day. It is not limited to nighttime conditions.

In summary, the fluttering sound is a key characteristic of HF scatter, distinguishing it from other propagation modes. Understanding this helps in identifying scatter propagation when operating on HF bands.