| 摘要 |
PROBLEM TO BE SOLVED: To recognize the presence/absence levels of an interfering wave and to speedily judge the change of channels by detecting and displaying the interfering wave. SOLUTION: The output of an AGC amplifier 6 is inputted to a distributor 15 and is distributed. One distributed signal is inputted to a band pass filter 9 in the same way as a conventional way. The other distributed signal is inputted to a band pass inhibition filter 16, and an output signal which is filtered and in which a desired wave is attenuated is inputted to a detection circuit 17. A detected detection voltage signal is inputted to a control circuit 14 and the interfering wave is displayed. The control circuit 14 controls the gains of the AGC amplifiers 4 and 6 based on the value of inputted detection voltage. When the interfering wave does not exist, it is not necessary to control the AGC amplifier 6. When the interfering wave exists, the circuit is prevented from being saturated by changing the gain characteristic of the input desired wave in accordance with the level of the interfering wave. Thus, the gain of the input desired wave corresponding to the level of the interfering wave can be set. |
