Quite easily, in one of two ways:
(1) use a 3-turn helix feed, as provided by Olde Antenna Labs and listed
in our online Tech Manual.
(2) put a second monopole feed in the existing cylindrical waveguide
feedhorn, 90 degrees spacially from the first, and feed the two to a
quadrature hybrid coupler.
More discussions of such hardware matters occur on the ARGUS email
discussion list, which is open to all SETI League members in good standing.
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H. Paul Shuch, Ph.D. Executive Director, The SETI League, Inc.
433 Liberty Street, PO Box 555, Little Ferry NJ 07643 USA
voice (201) 641-1770; fax (201) 641-1771; URL http://www.setileague.org/
email work: n6tx@setileague.org; home: drseti@usa.net
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