TACAN was designed in the 50's for aircraft caariers, the VOR will not work on a moving platform. As I remember from Navy Ground School back in 1966, the VOR has one stationary signal generator with one rotating signal generator and the TACAN has two rotating signal genrators based upon a 30 degree spacing overlaps, and one of the things you had to look for was a 30 degree bearing error in your TACAN when you did a TACAN bearing check on the ground. The DME portion is the same. VOR in VHF, TACAN is UHF.