What effect does ground has on a antenna?

For an antenna to work, the antenna must act like a capacitor or inductor because these two components will radiate when AC current with phase passes through. This is the foundation of radio technology.

So the ground does have an effect to the antenna, let's say you have a antenna tower on top of the mountain, the ground actually will reflects the signal and somewhat reduce or increase the gain. There is something called the radar equation where you can calculate if there's significant effect from the ground.

The antenna tower if it is on top of the mountain, the ground acts like a mirror, so the antenna is somewhat exists under the ground, i forgot the logic behind this...but there's a name for this effect.

did you mean ground as in ground plane of the antenna?. effect of the ground on the antenna pattern.

if u refer to image theory you will have a better idea of how ground effects the antenna performance. be specific there is so much that can be said about the effect of ground on antenna performance.

Regards
elchiquito

In general, an antenna is best defined in a "free space", with nothing around. We live, however, on the Earth, and for many antennas we use it as a relatively conductive plane. For low frequency operation it is not a good conductor, so we improve its conductivity by metal wires, etc. The conductive ground becomes an important part of an antenna, the radiation pattern is formed by it. In some cases it is used as a mirror, in others, as a conductive line, or a part of a waveguide...