| 摘要 |
PURPOSE:To improve acoustic sense, by providing a means to detect switching of antennas and changing properly the degree of stereo separation by a signal which detects the switching required for the detected antenna. CONSTITUTION:When the output of an AM wave detector 6 drops with deterioration of the received signal, the output of a comparator 14f of a switch detecting circuit 14 is changed to ''H'' level and then differentiated to be sent to a diode 17. An integration circuit consisting of a resistance 18 and a capacitor 19 integrates the negative component of the corresponding detecting signal owing to existence of a diode 17. Therefore, the potential of a joint C drops less as the switch detecting signals are produced more. The output B of an adder circuit 16, i.e., the control voltage for stereo separation degree is fed to a stereo demodulator 11 to control the stereo separation degree. The higher the level of the output signal B, the better the stereo separation degree. Therefore, when the switching of antennas is carried out frequently with deterioration of the received signal, the stereo separation degree drops much less than the level of a normal state. This reduces the noise of the input signal of the demodulator 11 and then improves the acoustic sense during reception. |
