| 摘要 |
PURPOSE:To prevent spurious radiation from being generated, by summing a signal level of a broad band part of an intermediate frequency amplifier stage and a signal level of a narrow band part and using the result as an AGC voltage of a high frequency amplifier stage, in an AGC circuit of a superheterodyne receiver. CONSTITUTION:The 1st detecting means (a level detector 11, a transistor TR, a semi-fixed resistor VR, a capacitor C1, a resistor R1) for detecting a signal level of the broad band part of the intermediate frequency amplifier stage 7, and the 2nd detecting means (a capacitor C2, a diode D1, a diode D2, a resistor R2 and a capacitor C3) for detecting a signal level of the narrow band part of the intermediate frequency amplifier stage 7, are provided. A potential obtained from the 2nd detecting means is added to a potential obtained at the 1st detecting means to form an AGC voltage for the high frequency amplifier stage 2. Then, even if an adjacent strong disturbing electromagnetic wave is incoming during the reception of a desired broadcast, the generation of spurious radiation is prevented and an effective AGC characteristic is formed. |
