*Question E9C13:
How does the radiation pattern of a horizontally polarized antenna vary with increasing height above ground?*  

*Correct Answer is  B: The takeoff angle of the lowest elevation lobe decreases*  

### AI Response: (may contain errors)  

The correct answer to the question about how the radiation pattern of a horizontally polarized antenna varies with increasing height above ground is:

**Correct Answer: B: The takeoff angle of the lowest elevation lobe decreases.**

### Explanation of the Correct Answer:
- As the height of a horizontally polarized antenna increases, the takeoff angle of the lowest elevation lobe decreases. This means that the antenna will radiate signals at lower angles relative to the horizon.
- This occurs because a higher antenna has a clearer line of sight to the horizon, allowing it to radiate more effectively at lower angles. This is particularly beneficial for long-distance communication, as signals can travel further without being obstructed by the ground.

### Why the Other Choices are Incorrect:
- **A: The takeoff angle of the lowest elevation lobe increases.**
  - This is incorrect because increasing the height of the antenna actually lowers the takeoff angle, not increases it. A higher antenna has a better radiation pattern for lower angles.

- **C: The horizontal beamwidth increases.**
  - This is incorrect because the horizontal beamwidth typically decreases as the height of the antenna increases. A higher antenna tends to focus its energy more narrowly in the horizontal plane.

- **D: The horizontal beamwidth decreases.**
  - This statement is actually true, but it is not the correct answer to the question asked. The question specifically focuses on the takeoff angle, not the beamwidth.

### Useful Rules of Thumb:
- **Height and Takeoff Angle:** As a general rule, the higher the antenna, the lower the takeoff angle of the lowest lobe. This is beneficial for long-distance communication.
- **Antenna Gain and Height:** Higher antennas can also achieve greater gain due to reduced ground losses and improved line-of-sight propagation.

Understanding these concepts will help you grasp how antenna height affects radiation patterns, which is crucial for effective amateur radio operation.