| 摘要 |
PURPOSE:To make a high frequency input level and the deflectio of a reception sensitivity indication meter proportional over a wide range by detecting the rise of a reception signal electric field strength for a prescribed level or over and using the detecting signal so as to control the gain of the meter drive circuit. CONSTITUTION:A detection output VS proportional to a reception signal f1 is obtained from an intermediate frequency signal f1'' of a radio receiver, the signal VS is fed to a drive circuit 23 driving an S meter of the reception sensitivity indicator so as to deflect the meter 20. When the reception electric field strength is increased and an RFAGC12 is operated, although the deflection of the meter is saturated, an RFAGC SIGNAL FV is inputted to a comparator 24 and compared with a reference voltage VREF. When the level of the signal FV is higher than the reference voltage VREF, the comparator 24 outputs the signal VC, a transistor (TR) Q4 of the circuit 23 is conductive, the gain of the circuit 23 is changed in esponse to the electric field strength of the reception signal f1 so as to make the deflection of the S meter 20 proportional to the electric field strength.
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