PURPOSE: To provide an optimum reception state at all times by converting the data of a storage circuit to a control voltage in a D/A conversion circuit, applying it to a detection circuit and correcting the S curve characteristics of the detection circuit.

CONSTITUTION: When a power supply is applied, a control circuit 10 reads correction data from the prescribed address of the storage circuit 11 and supplies them to the D/A conversion circuit 8. Thus, the control voltage for correction is supplied from the circuit 8 to the detection circuit 5. The capacitance of a varicap diode fluctuates based on the applied control voltage and the resonance frequency of an LC circuit fluctuates as well. Thus, a phase is adjusted so as to be shifted accurately for 90 degrees and the S curve characteristics of the detection circuit 5 are corrected. During an operation, the control voltage is applied to the detection circuit 5 at all times and the S curve characteristics are kept accurately outputted. In such a manner, since the correct S curve characteristics can be obtained at all times, more accurate automatic tuning can be performed and sound signals with improved distortion ratio and S/N can be obtained.