English: Diagram of a ground plane antenna, a common omnidirectional monopole antenna used at VHF and UHF frequencies. It consists of a vertical whip antenna one quarter wavelength long, with 3 or 4 quarter wave rods extending from the base electrically connected to the ground side of the transmission line. The ground rods create a ground plane under the antenna which increases the gain. The ground rods may extend horizontally from the base, but in antennas fed by coaxial cable as shown here they are usually sloped downward to increase the radiation resistance of the antenna from the 36 ohms of a quarter wave monopole closer to 50 ohms, so the antenna will be a better impedance match to standard 50 ohm coaxial cable.