A magnetic resonance (MR) system comprises a main magnetic field and an RF power amplifier for generating an RF field in a first RF band, the arrangement further comprising at least one magnetic field probe (2), said magnetic field probe comprising a MR active probe substance, means for pulsed MR excitation of said probe substance (4) in a second RF band and means for receiving a probe MR signal in the second RF band generated by said probe substance. In order to improve performance of the system, the latter comprises means for recording the output signal of the RF power amplifier in said second RF band, and means for subtracting from said probe MR signal an interfering signal contribution contained in said recorded RF amplifier output signal.