Short wave broadcasting antenna, Moosbrunn, Austria. This is a curtain antenna, a high gain directional wire antenna used on the high frequency (HF) bands by shortwave broadcasting stations for long distance international broadcasting. It consists of an array of wire dipoles fed in phase, in front of a vertical "curtain" reflector consisting of closely spaced parallel wires. It radiates a unidirectional beam of radio waves at a shallow angle above the horizon. The radio waves are reflected by the ionosphere back to earth beyond the horizon to cover a listening area in another country. In this example the entire antenna is mounted on a truss that rotates on a spindle, allowing the direction of the beam to be changed.