| 摘要 |
PURPOSE:To obtain an excellent stable reception picture in the diversity reception by controlling the switching operation of a switch means in response to a level of a noise component detected from a reception video signal. CONSTITUTION:An output signal of a video amplifier circuit 3 is clamped by a clamp circuit 11 and a noise gate circuit 13 extracts a pedestal of an equivalent pulse section after a vertical synchronizing signal. The pedestal is amplified (14) and given to a noise level detection circuit 15 to obtain a DC voltage in response to a noise level and the DC voltage is amplified (16) and given to a sample holding circuit 17. The noise level subjected to sample holding is compared with a threshold value by a comparator circuit 20. The circuit 20 gives a high level output to a discrimination circuit 8 when the noise voltage level is higher than the threshold value and gives a low level output when lower. The circuit 8 inhibits the output of the antenna switching timing pulse to the antenna selection circuit 10 and outputs the pulse at the high level state to apply diversity reception.
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