Offset dish antenna

The purpose of this design is to move the feed antenna and its supports out of the path of the incoming radio waves.

In an ordinary front-fed dish antenna, the feed structure and its supports are located in the path of the incoming beam of radio waves, partially obstructing them, casting a "shadow" on the dish, reducing the radio power received.

In the offset design, the feed is positioned outside the area of the beam, usually below it on a boom sticking out from the bottom edge of the dish.

Because of the limited transmitter power provided by their solar cells, satellite antennas must function as efficiently as possible.

Before the 1970s offset designs were mostly limited to radar antennas, which required asymmetric reflectors anyway to create shaped beams.