English: A mast radiator antenna for an AM radio station transmitter in Chapel Hill, North Carolina. The radio frequency current from the transmitter is applied directly to the steel lattice tower, which acts as a monopole antenna element. The tower is supported at its base by a massive porcelain insulator, which insulates it from the ground. The high voltage on the tower can deliver a dangerous shock to anyone that touches it, so it is surrounded by a fence to keep people out. The white shed is called a helix house and contains an antenna tuner matching network to match the impedance of the antenna to the transmitter to allow power to be transferred efficiently to the antenna. The mast is supported by guy wires (faint), which have strain insulators in them to prevent the high voltage on the tower from being conducted to ground.