*Question E3B13:
What type of polarization is supported by ground-wave propagation?*  

*Correct Answer is  A: Vertical*  

### AI Response: (may contain errors)  

Ground-wave propagation primarily supports vertical polarization. Here's a breakdown of why this is the correct answer and why the other options are not suitable:

### Correct Answer: Vertical

- **Reasoning**: Ground-wave propagation occurs when radio waves travel along the surface of the Earth. Vertical polarization is effective in this mode because it allows the radio waves to follow the curvature of the Earth and minimizes losses due to ground reflection. Vertical antennas are typically used for this type of propagation, as they can efficiently couple with the ground.

### Incorrect Choices:

- **A: Horizontal**: 
  - While horizontal polarization can be used for some types of propagation, it is less effective for ground-wave propagation. Horizontal waves tend to radiate away from the ground and do not couple as well with the Earth's surface, leading to increased losses.

- **C: Circular**: 
  - Circular polarization is used in specific applications, such as satellite communications, but it is not typical for ground-wave propagation. Circularly polarized waves do not follow the ground as effectively as vertically polarized waves.

- **D: Elliptical**: 
  - Elliptical polarization is a more complex form that can be thought of as a combination of linear polarizations. Like circular polarization, it is not commonly used for ground-wave propagation, which favors simpler vertical polarization for effective coupling with the ground.

### Summary

- Ground-wave propagation is best supported by **vertical polarization** due to its ability to follow the Earth's surface and minimize losses.
- Horizontal, circular, and elliptical polarizations are less effective for this type of propagation.

This understanding is crucial for the Extra Class exam, as it highlights the practical applications of polarization in radio communications.