A ground plane antenna (GPA), also referred to as a monopole antenna, is a variant of a vertically mounted dipole antenna. It is a bisected, stretched half-wave dipole consisting of a lambda quarter antenna element designated radial.
A monopole antenna can have multiple radials that go to the antenna impedance. The second half of the monopole antenna is formed by the electrically conducting ground plane. The radiation pattern of the ground plane antenna exhibits an omnidirectional characteristic with a circular main lobe that is radiated equally in all directions. Frequencies below 50 MHz have a larger vertical propagation compared to a dipole antenna.