English: Front view of antennas of the Allan Telescope Array, a radio telescope for combined radio astronomy and SETI (search for extraterrestrial intelligence) research being built by the University of California at Berkeley, outside San Francisco. The first phase, consisting of 42 6-meter dish antennas shown here, was completed in 2007. Eventually it will have 350 antennas. This type of antenna is called an offset Gregorian design. The incoming radio waves are reflected by the large parabolic dish onto a secondary parabolic reflector in front of the dish, and then into a feed horn. A metal shroud along the bottom of the secondary reflector shields the antenna from ground noise. It covers the frequency range from 0.5 to 11.2 GHz.