An arrangement for connecting an additional antenna to a portable radio device (RD) having an internal planar antenna. Energy for the additional antenna is taken from the near field of the planar antenna, the coupling elements being provided by conductors (311, 312) located outside the covering of the radio device and following the conductive branches (B1, B2) of the radiating plane (RPL) of the planar antenna. The arrangement further comprises a conductive plate (320) located in front of and parallel to the ground plane (GND) in the radio device to take energy from the field of the ground plane. The inner conductor of the cable (330) for the additional antenna is galvanically connected to the conductors placed over the planar antenna, and the sheath is galvanically connected to the conductive plate (320) near the connection point of the inner conductor.