| 摘要 |
PURPOSE:To improve the characteristics by omitting the manual gain control to secure an ample gain reduction with by applying AGC to both the IF amplification part of the UHF system of the TV picture receiver and the high frequency amplification part of the UHF system. CONSTITUTION:The output of tuner 1 is applied to video IF amplifier 12, and the output of amplifier 12 is applied to IFAGC circuit 11 to control circuit 12 by the output of circuit 11. When the electric field becomes intensive even more, RFAGC circuit 13 is controlled by the output of circuit 11. Then the output of circuit 13 is applied to UIFAGC circuit 18 of control system in the UHF system which is provided newly at the reception time of UHF. And the output of circuit 18 is applied to UIF system 16 to control the IF amplifier as well as to delay circuit 19 to drive URFAGC circuit 20 via the output which is delayed by a fixed time. And then the high frequency amplification part of system 16 is controlled by the output of circuit 20. As a result, an ample gain reduction width can be obtained without giving any manual adjustment, thus improving the output characteristics of the video signal. |
