*Question E3B03:
At what time of day is transequatorial propagation most likely to occur?*  

*Correct Answer is  C: Afternoon or early evening*  

### AI Response: (may contain errors)  

Transequatorial propagation is a radio propagation phenomenon that occurs when radio waves travel over the equator, often taking advantage of the ionosphere's conditions. 

### Correct Answer: Afternoon or early evening

1. **Why the correct answer is correct:**
   - Transequatorial propagation is most effective during the afternoon and early evening due to increased ionization in the ionosphere. 
   - The sun's position at these times enhances the ionization levels, allowing for better reflection of radio waves, particularly in the HF (high frequency) bands. 

### Why the other choices are incorrect:

2. **Morning:**
   - In the morning, the ionosphere is still recovering from the night, and ionization levels are lower, making propagation less effective.

3. **Noon:**
   - While the sun is directly overhead, the ionosphere can become too ionized, leading to a phenomenon called "over-ionization," which can actually degrade propagation conditions.

4. **Late at night:**
   - At night, the ionosphere loses ionization, which significantly reduces the chances of transequatorial propagation. The lower ionization levels mean that radio waves are less likely to be reflected effectively.

### Useful Rules of Thumb:
- **Propagation Conditions:**
  - Higher ionization levels generally improve HF propagation.
  - Afternoon and early evening are optimal for transequatorial propagation due to the sun's angle and its effect on ionization.

Understanding these factors will help you predict when transequatorial propagation is most likely to occur, which is crucial for effective communication in amateur radio.