| 摘要 |
PURPOSE:To ensure the satisfactory muting operations in a channel selection mode, a detuning mode, etc. despite the presence of a broadcast station having an extremely large input field intensity without using a special noise detecting circuit and with a simple and inexpensive constitution, by providing the frequency characteristics to detect also the high band noise component when the output signal of an FM wave detecting circuit is detected. CONSTITUTION:A broadcast station has an extremely large input field intensity, and the output signal of an intermediate frequency amplifier circuit 5 is increased up to the bottom part level of the frequency characteristics of an intermediate frequency signal owing to the blocking characteristics of a front end, the characteristics of an intermediate frequency filter, the earth state, etc. Then a noise signal of a high level is obtained at a frequency band outside an S curve frequency range at the output side of an FM wave detecting circuit 6 even in case the level of said bottom part exceeds a prescribed level Vs. The high band noise component of said noise signal is supplied to a comparator 11d via a buffer amplifier circuit 11a. Thus a muting circuit 8 has a muting ON state. |
