Abstract: An antenna arrangement for transmitting at least two frequencies over a single antenna element, the length of which is selected as a fraction, for example, ⅝ths, of the wavelength of the lower of the said at least two frequency. The higher frequencies are transmitted via slots formed in the wall of the waveguide forming the antenna element. The antenna element is in the form of, at least, a semi-rigid structure which includes a waveguide antenna formed integrally with a waveguide feed line to provide a single waveguide unit, the internal structure of the single waveguide unit being used as a waveguide for the higher frequencies which are transmitted via the slots in the wall of the waveguide.