Abstract: Relatively small omnidirectional antennas (2,3) with sufficient antenna impedance for exchanging radio frequency signals are provided with two parallel elements (21,22) coupled to each other via their outer ends. Each element (21,22) comprises two subelements (23,24,25,26) separated by a gap (27,28). The elements (21,22) have lengths smaller than half the wavelength of the radio frequency signals. The antennas (2,3) do not need to be operated against a ground surface, and can be used in a non-horizontal position. The elements (21,22) are planar elements. The antennas (2,3) further comprise two further elements (41,42) located in a plane parallel to a plane of the elements (21,22). This increases the impedance and improves the return loss of the antennas (2,3). One of the further elements (41) comprises two sub-elements (43,44) separated by a gap (47), to realise a simulated return loss with one dip.