What is gain in an antenna?
Gain in an antenna is not the creation of power, but rather a simple refocusing of energy from all directions to a specific direction. Gain is measured in decibels (dB). Ideal vertical plane radiation pattern showing the difference in antenna radiator element lengths.Vertical antennas are in fact quite directional, except in the horizontal or azimuth plane. The figure to the left shows the radiation pattern of three different length radiating antenna elements. Note that the quarter wavelength antenna has the highest angle of radiation; however, it also has the lowest gain of the three cases. The 5/8 wavelength antenna has both the lowest angle of radiation and the highest gain, which gives superior performance at sea level.
