Antenna tuning hut

An antenna tuning hut or helix house is a small shed at the base of a longwave or mediumwave radio transmitting antenna. It contains antenna tuner radio equipment for coupling the power from the feedline to the antenna.[1] The building may also contain lightning protection devices and power transformers for aircraft warning light on the tower. The radio transmitter which generates the radio frequency current which powers the antenna is generally located away from the antenna, to prevent the powerful radio waves from interfering with the sensitive transmitter circuits. The radio frequency current from the transmitter is supplied to the antenna through a cable called the feedline. The antenna tuning hut contains a matching network consisting of capacitors and inductors (coils) needed to match the antenna's impedance with the feedline, so power is transferred efficiently to the antenna. The inductors, consisting of large helixes of wire, give it the common name helix house.

Antenna tuning hut of the backup tower for Blosenbergturm in Beromünster.

Antenna tuning hut under the backup tower in Beromünster.

Alternative names include 'antenna tuning house' or, simply, 'doghouse'. The powerful radio waves near the antenna can be a hazard to workers. The interior of the antenna tuning hut is typically covered with copper or aluminum, in order to control stray radiation. In operation the components can have a voltage of several hundred thousand volts.