Abstract: The invention is concerned with the provision of a dipole radiator for feeding a parabolic reflector and provides a half wave dipole arranged at the mouth of a shallow cavity. The cavity is preferably circular with a diameter approximately three times its depth. In an example of linearly polarised radiator a cylindrical cavity is provided having a diameter of 0.72.lambda. and a height of 0.26.lambda. and the half wave dipole element is positioned 0.26.lambda. above the base of the cavity so that the dipole element extends beyond the cavity. In an example of circularly polarised radiator two crossed half wave dipole elements are provided, one of which is arranged to be inductive and the other of which is arranged to be capacitive. The cylindrical cavity has a diameter of 0.66.lambda. and a height of 0.28.lambda. and the crossed dipole elements are positioned 0.22.lambda. above the base of the cavity so as to lie flush with the mouth of the cavity.