George Ruch wrote

Operating frequencies dictate the size of the antenna array.
Compare this picture of a TACAN site at
http://en.wikipedia.org/wiki/TACAN with this one of a VOR site
at http://en.wikipedia.org/wiki/VOR.

Actually George, the first picture is a VORTAC, a TACAN and VOR
installation. The TACAN is just the round cylinder part and that
is what makes it so easy to mount onboard a ship.

Bob Moore