An antenna

Antenna (radio)

An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...

 rotator is a device which is used to change the orientation of a directional antenna

Directional antenna

A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced interference from unwanted sources....

. Most antenna rotators have two parts, the rotator unit and the controller. The controller is normally placed near the equipment which the antenna is connected to, while the rotator is mounted on the antenna mast directly below the antenna.

Rotators are commonly used in amateur radio

Amateur radio

Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...

 and military communications installations. They are also used with TV and FM

FM broadcasting

FM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"...

 antennas, where stations are available from multiple directions, as the cost of a rotator is significantly less than that of installing a second antenna to receive stations from multiple directions.

Rotators are manufactured for different sizes of antennas and installations. For example, a consumer TV antenna rotator has enough power to turn a TV/FM or small Ham antenna. These units typically cost around US$70.

Heavy-duty Ham rotators are designed to turn extremely large, heavy, high frequency

High frequency

High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...

 (shortwave

Shortwave

Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...

) beam antennas, but cost hundreds and possibly thousands of dollars.