Question
How does the radiation pattern of a horizontally polarized antenna vary with increasing height above ground?
Answer Options
- A) The takeoff angle of the lowest elevation lobe increases
- B) The takeoff angle of the lowest elevation lobe decreases
- C) The horizontal beamwidth increases
- D) The horizontal beamwidth decreases
Correct Answer: B
Explanation
For any antenna operating near the ground, the radiation pattern in the vertical plane (elevation pattern) is a function of its height. This pattern is created by the combination of the direct signal leaving the antenna and the signal reflecting off the ground beneath it (ground gain).
As the height of a horizontally polarized antenna is increased, the distance between the antenna and the ground reflection point increases. This causes the angle of the main lobe to decrease, meaning the takeoff angle of the lowest elevation lobe decreases. Lower takeoff angles are highly desirable for long-distance communication because more energy will be reflected or refracted by the ionosphere.
This topic was automatically created to facilitate community discussion about this exam question. Feel free to share study tips, memory tricks, or additional explanations!