Broadway shows on tap for new cable TV channel

The Entertainment Channel, formerly called RCTV, a joint venture of Rockefeller Center Cable Inc. and RCA Cable Inc., has linked up RKO/Nederlander to present Broadway shows on tape.

According to Monitor TV critic Arthur Unger, the licensing agreement will offer five productions at first, possibly including ''Sweeney Todd,'' ''I Do, I Do,'' ''Lena Horne: the Lady and Her Music,'' ''The Canterbury Tales,'' and ''Emlyn Williams as Charles Dickens.''

Launching date for the Entertainment Channel is June 4.