Question
What does the term “ground gain” mean?
Answer Options
- A) The change in signal strength caused by grounding the antenna
- B) The gain of the antenna with respect to a dipole at ground level
- C) To force net gain to 0 dB by grounding part of the antenna
- D) An increase in signal strength from ground reflections in the environment of the antenna
Correct Answer: D
Explanation
The radiation pattern of an antenna, particularly its gain and vertical (elevation) angle, is significantly influenced by the effect of the Earth’s surface beneath it. This effect is not due to conductive grounding, but to the physics of radio waves reflecting off the ground.
Ground gain refers to an increase in signal strength from ground reflections in the environment of the antenna. The radiated signal hits the ground and reflects toward the distant receiving station. The direct signal and the reflected signal combine at the receiver. When these signals combine constructively (in phase) at a specific vertical angle, the overall gain is enhanced, often by as much as 5 dB to 6 dB (especially for low-angle radiation over highly conductive ground like saltwater).
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