File:Picture bwg.gif

English: Drawing of a beam waveguide antenna, a type of parabolic antenna used in large radio telescopes and satellite ground stations. In the beam waveguide antenna, the incoming radio waves collected by the large primary reflector dish are reflected by secondary reflectors in a long path through the structure (red) to the base of the antenna, where they are received by a small feed antenna in a "feed house" at ground level. This design is an alternative to the common design used in small dish antennas called "front feed", in which the feed antenna itself is suspended in front of the dish. Beam waveguide antennas are used in high gain antennas for use in space communication, where the feed electronics is too bulky and delicate to be mounted on the boom in front of the antenna, or must be serviced often, as with low-noise cryogenic amplifiers which require frequent filling with liquid nitrogen.