| 摘要 |
PURPOSE:To avoid the unnaturalness at scanning, by the squelch with the signal obtained from noise from the FM detection circuit in operation state at FM and AM reception with rectification. CONSTITUTION:At non-signal, at FM and AM reception, the noise appeared at the terminal 9, i.e., the output terminal of the FM detection circuit 14, is applied to the voice volume VR1 and active BPF21. The BPF21 detects noise outside the voice band, the noise is rectified at the diode D3 and applied to the input terminal of the squelch switching circuit 24. Since the AGC at AM side is not effective at non-signal, RFAMP and IFAMP are at maximum gain state, and since the noise voltage from the FM detection circuit 14 is equal at FM and AM reception, the operating point of squelch can be set to the same position at FM and AM reception. |
