A heterodyne receiver comprising a gain controllable RF mixer (14) which has a first input connected to a first local oscillator (16) and a second input connected to an RF input. The receiver comprises a peak detector (38) which detects a peak value of an input signal at the second input of the HF mixer and generates a digital control signal if it is determined that the peak value of the input signal is above a predetermined level. A digital automatic gain control circuit (34) decreases upon reception of the digital control signal the gain of the RF mixer.