antenna adaptor for Roksan Caspian

I recently bought a Roksan Caspian tuner, on the used market. It did not come with an antenna. I planned on using my Godar flat antenna, which has a standard (BNC?) connector. However, the Caspian tuner has a different, larger connector. I tried Radio Shtick, but they didn't have an adaptor that would fit the tuner. Anyone know what the connector on the back of the Caspian is called, and where I might find an adaptor that would enable me to link to my Godar antenna? Thanks! Ben
email MayAudio or Roksan, they respond usually. Or Mike Godar or Gene Rubin Audio in Ventura ? county CA. Gene carries the Godar. Parts Express can sometimes help also.