| 摘要 |
PURPOSE:To attain the best reception condition for both an FM broadcast and a wireless microphone by changing over a muting-off band width into a narrow band width or a wide band width in response to the mode changeover. CONSTITUTION:When an FM boradcast is inputted to an antenna 1 with a switch S3 by connecting interlockingly a contact 28 and with switches S1, S2 to contacts 29, 20 respectively, an IF signal is inputted to a detecting circuit 5. Further, an output signal for muting-off of a band width of + or -100kHz to the center frequency is given at an output side of a narrow band muting control circuit 8 and only the IF signal within this band width is detected and outputted via a muting circuit 6. On the other hand, when a signal of a wireless microphone is received, the switches S1, S2 are put to contacts 22, 17 respectively. A wide band muting control circuit 9 detects the level of a band width of + or -500kHz to the center frequency of the IF signal and turns on a transistor 13 of a changeover switch circuit 11 during this time. |
