What is a Ground Plane Vertical Antenna in Amateur Radio?

What is a Ground Plane Vertical Antenna in Amateur Radio?

Ground plane vertical antenna is often used for VHF transmission in Amateur Radio. The vertical portion of the antenna is quarter wave-length. Usually the ground plane is formed by four equally spaced radials, of quarter wave-length each. Central conductor of the coaxial cable is connected to the vertical element and the metallic sleeve of the coax is connected to the radials which form the ground plane.

Another option is to have a conducting ground plane of at least quarter wave-length in radius. This can be considered for a mobile antenna mounted on top of a metallic vehicle body. It is an omnidirectional antenna which radiates equally in all directions. Feed point impedance is usually half that of a dipole, about 36 Ohms. SWR will be less than 2:1 when connected with a 50 Ohms coaxial cable.