An arrangement for filtering the transmitting signals in a radio device using frequency division duplex. In a radio transmitter, in which the transmitting signal is divided to a plurality of antennas (ANT1 , ANT2, ANT3) radiating to different sectors, the filtering required in transmitting is mostly carried out by a shared transmitting filter (240) before the transmitting signal is divided. The rest of the filtering is carried out separately on each partial transmitting signal (T1; T2; T3) in the reduced transmitting side (TXF1 ; TXF2; TXF3) of the duplex filter. The filters and the divider (250) preferably form an integrated filter unit, in which they are connected to each other by simple coupling elements. The space required by the filters of the antenna end of the radio device is significantly reduced, and the material and assembly costs of the antenna end in production are reduced.