The new feed system for the SETI Institute Woodbury site 30-m-diameter Cassegrain antenna

The 30-m-diameter C-band Cassegrain antenna on the Woodbury site (near Georgia, Atlanta) is used by the SETI Institute as a verification station for SETI observations. We have supplied a feed system to enable this antenna to now operate from 1-3 GHz with a single feed configuration, consisting of a feed-horn and an orthomode transducer (OMT). While it was the norm to provide several feeds to cover such a bandwidth, and switch-in the individual feeds as required, there are obvious advantages in having only one feed system. In addition to the 1-3 GHz SETI requirement, the antenna will also, in the future, be required to operate up to 7 GHz. The feed horn was designed to cover the 1-7 GHz range; the limit to 3 GHz is in the performance of the OMT connected to the feed horn. Nevertheless, at frequencies above 3 GHz, in particular 4.2 and 5-6 GHz, reduced performance on a single polarization (where a return loss as low as 3 dB was tolerable) was of interest. To this end, measurements were taken to 7 GHz.