| 摘要 |
PURPOSE:To improve the S/N by adding a sound output signal to a low frequency amplifier through a low pass filter to be selected. CONSTITUTION:A noise component only of an output from a frequency discriminator 1 is amplified and rectified by a noise amplifier 2 and the result is fed to a comparator section 3. Moreover, an input terminal of a low pass filter 5 is connected to the output of the frequency discriminator 1 via a buffer for an attenuator and the output terminal is connected to an input terminal of a low frequency amplifier 6 having a wide band characteristic. Thus, as the RF level is decreased, the noise level is increased and the control signal is outputted from each comparator as comparators 31, 32 and comparators 31, 32, 33 and capacitors C1, C2 and capacitors C1, C2, C3 are connected to ground in this order. Thus, the low sound is emphasized at a frequency with bad S/N, the noise is decreased and the reception sensitivity is improved practically. |
