Monopoles in Kheraj refer to monopole antenna, which are a range of radio antennas. They feature a straight rod-shaped conductor, which is usually mounted perpendicularly over a conductive surface known as the ground plane. The types of monopole antennas include helical, mast radiator, rubber ducky, whip, mast radiator and ground plane antennas. The monopole is a resonant antenna – the rod acts as a resonator for radio waves, with oscillating standing waves of current and voltage along its length. The wavelength of the radio waves used with the antenna determines the length of the antenna. The most commonly used antenna is quarter-wave monopole.