PURPOSE: To enable the gain control of wide band, by controlling the conversion circuit in frequency convering the intermediate frequency signal and the circuit in frequency converting the converted frequency again with the output of the same local oscillator to pick up the control voltage from a given frequency.

CONSTITUTION: The signal at intermediate frequency fed to the input terminal A is fed to the frequency conversion circuit 2 via the gain control circuit 1, frequency conversion is made with the frequency produced from the local oscillation circuit 7, the signal in frequency conversion is branched with the branch circuit 3 and outputted to the output terminal B and fed to the frequency conversion circuit 4. To the conversion circuit 4, the oscillation frequency of the same oscillator 7 as being fed to the conversion circuit 2 is fed, the signal of the same frequency as the input intermediate frequency is fed to the detection circuit 5, the signal having required band is picked up at the detection circuit 5, the output of the circuit 5 is fed to the control circuit 6, and the gain control of the gain control circuit 1 is controlled with required band width.