| 摘要 |
PURPOSE:To improve the disturbing wave dependent upon intermodulation and prevent S/N degradation, by detecting the signal level after intermediate frequency filter passage and by providing a switching circuit which makes an AGC circuit unoperated if the detection signal level is a prescribed value or less. CONSTITUTION:AM detector circuit 12 and switching circuit 13 are provided in the output side of intermediate frequency filter circuit 7 of a radio receiver. When the input level of the desired receiving signal to antenna 1 is a prescribed value or more, the DC voltage detected by circuit 12 turns on circuit 13 to operate AGC circuit 10. During the AGC operation time, the signal of the disturbing frequency is suppressed, and intermodulation disturbance is improved. When the antenna input of the desired receiving signal is a prescribed value or less, the DC voltage detected by circuit 12 is small, and therefore, electricity is turned off in circuit 13, and circuit 10 becomes unoperated. By making AGC unoperated, degradation of S/N can be prevented. |
