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Thanks for sending along the latest SearchLites. I found the article about the Allen Telescope Array interesting. I wonder if you could explain the ATA dish design. I've seen pictures of the array, and find the design intriguing. Doc, North Dakota The Doctor Responds: I'm glad you're enjoying SearchLites, Doc. The ATA dishes are Gregorian antennas. They use a ~6 meter offset-fed primary mirror, which reflects incoming signals onto a ~2 meter secondary reflector which is mounted outside of the focal point. The secondary mirror in turn reflects the signals to a broadband log-periodic feed, which contains a cryogenically cooled combination balun (balanced-to-unbalanced transformer) and an extremely broadband, ultra-low-noise preamplifier. All very high efficiency, very complicated, and very expensive!
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