Yagi antenna gain refers to the ratio of the power density of signals generated by the actual antenna and the ideal radiating element at the same point in space under the condition of equal input power. It quantitatively describes the degree of concentrated input power of the antenna. The gain is obviously closely related to the antenna pattern. The narrower the main lobe, the smaller the sidelobe and the higher the gain.
Compared with the basic half-wave dipole or folded dipole antenna, Yagi antenna has the advantages of high gain, strong directivity, anti-interference, long acting distance, simple structure, readily available materials, low price, small wind shield, lightness and firmness, and convenient erection.