There is described a dielectric polariser for a bicone antenna. The polariser can include radiating vanes that are spaced circumferentially around an aperture of the bicone antenna. The vanes are orientated at 45° to the polarised waves propagated from the antenna in order to circularly polarise the linearly polarised waves. The polariser can be configured for manufacture using a 3D printing process. Surfaces of a central hub of the polariser can be metallised to provide the radiating surfaces of the antenna. This removes the need to use separate antenna elements. Alternative arrangements of 3D printed dielectric polariser are disclosed for use with antenna horns.