*Question E9C11:
How is the far-field elevation pattern of a vertically polarized antenna affected by being mounted over seawater versus soil?*  

*Correct Answer is  D: Radiation at low angles increases*  

### AI Response: (may contain errors)  

When considering the far-field elevation pattern of a vertically polarized antenna, the type of ground beneath the antenna plays a significant role in its radiation characteristics.

### Correct Answer: D - Radiation at low angles increases

1. **Why the correct answer is correct:**
   - When a vertically polarized antenna is mounted over seawater, the ground reflection is much more effective than over soil. Seawater has a lower impedance and higher conductivity, which enhances the radiation at low angles. This results in increased radiation efficiency and a stronger signal being transmitted or received at lower angles, making it more effective for long-distance communication.

### Why the other choices are incorrect:

2. **A: Radiation at low angles decreases**
   - This is incorrect because, as mentioned, seawater enhances low-angle radiation due to its conductive properties. Therefore, low-angle radiation does not decrease; it actually increases.

3. **B: Additional lobes appear at higher elevation angles**
   - This choice is incorrect because the presence of additional lobes at higher elevation angles is not a typical effect of changing the ground type. Instead, the pattern becomes more focused at low angles over seawater.

4. **C: Separate elevation lobes will combine into a single lobe**
   - This is also incorrect. The elevation pattern over seawater tends to produce a more pronounced low-angle lobe rather than combining separate lobes. The ground's properties affect the radiation pattern but do not typically lead to the merging of lobes.

### Useful Concepts:
- **Ground Reflection:** The quality of the ground (conductivity and permittivity) affects how well the antenna's radiation is reflected back towards the sky.
- **Antenna Gain:** The gain of the antenna can be affected by the ground type, with better ground conditions (like seawater) leading to improved low-angle radiation.

In summary, mounting a vertically polarized antenna over seawater increases radiation at low angles due to the conductive nature of seawater, enhancing the antenna's performance for long-distance communication.