Abstract: A secondary radar transponder on a mobile target has an antenna arrangement which can receive interrogation signals from all directions and radiate reply signals. The antenna arrangement includes several individual antennas, each of which, with its primary lobe, covers a specific sector of the entire 360.degree. range and is connected to a receiver, so that through receiving level comparison, that particular sector from which the interrogation signal incides can be ascertained. The reply signal is then radiated only by the individual antenna covering that particular sector. The transponder is particularly suited for identification friend-foe (IFF) purposes.