An apparatus for communicating with a radiation therapy device comprises a first plurality of omnidirectional radio antennas 212, 214 mounted upon a rotor 202, and a second plurality of omnidirectional radio antennas 216, 218 positioned at respective fixed locations off the rotor. The first plurality of antennas 212, 214 may be substantially equally spaced around the axis of rotation of the rotor 202. The first plurality of antennas 212, 214 and the second plurality of antennas 216, 218 are positioned so as to allow line-of-sight radio communication between at least one of the first plurality of antennas and at least one of the second plurality of antennas at all angles of rotation of the rotor 202.
