Feed

The feed collects the RF radiation. All feeds and receivers are available at any time, and are selected by subreflector motion controlled by the computer. The shaped subreflector illuminates all feeds above 1 GHz; these feeds are located on a ring at the Cassegrain focus, and changes from one feed to another (hence changes in observing band) take only a few seconds. In addition, a permanently installed dichroic enables simultaneous 2.3/8.4 GHz observations. The 330 and 610 MHz feeds are crossed dipoles mounted on the subreflector near prime focus. Therefore, it is possible to make simultaneous 330/610 MHz observations.