There is an interesting site about simple radio telescopes being used as interferometers. see
http://intro.fringes.org/
It has it's origin on a simple interferometer that was built at the ATCA at Narrabri in 2001. (
http://www.narrabri.atnf.csiro.au/~bro764/YASI.html )
I saw it at the time. It was essentially a wire clothes line but it worked.
Take a look at the two sites for some ideas.
Terry B