This invention relates to radio antennae, and in particular to dielectric-clad antennae of the kind comprising a length of conductor the electrical length of which is effectively increased by a cladding of dielectric material. The disclosure describes how the physical height of an antenna, typically an HF or VHF wire monopole antenna can be reduced in relation to its electrical length by means of a thin cladding of dielectric material having a relative magnetic permeability substantially greater than unity, e.g. ferrite. By selecting a material having a relative magnetic permeability substantially greater than its relative dielectric permittivity, a given reduction in antenna height can be achieved with a much thinner cladding than can be achieved using conventional materials.