Abstract: A radio communications apparatus employs a training routine for optimizing performance and has a modulator (64, 66) to modulate a radio channel with digital information, to provide baseband signals (I, Q) at a first data rate. A power amplifier (36) amplifies signals fed from the modulator. A feedback loop (40, 42, 44, 30) samples the output signals of the power amplifier and adjusts at least one of the amplitude and phase of the baseband signals to compensate for distortion introduced by the power amplifier. The data rate of the baseband signals is reduced during the training routine to reduce adjacent channel transmissions.