| 摘要 |
PURPOSE:To eliminate the generation of unnecessary spurious components from a squelch circuit, by providing an AGC circuit in the squelch circuit. CONSTITUTION:When the input level of a high frequency is lower than a squelch level, the high-frequency signal from a branching circuit 7 is amplified through a gain controlling circuit 13 to operate a relay circuit 15, and a contact 16 is connected to the side of a contact A. At this time, the output of a DC amplifier 6 approximates its maximum, and a gain controlling circuit 13 is controlled to the maximum gain. Meanwhile, the gain of a gain controlling circuit 2 is held down, and the high-frequency output from an output terminal (b) is broken. When the input level becomes higher than the squelch level, the output of a detecting circuit 9 is increased to switch the contact 16 of the relay circuit 15 to the side of a contact B. The gain of the gain controlling circuit 2 is increased, and the output is generated from the terminal (b). When the input level becomes higher furthermore, the gain of the gain controlling circuit 2 is reduced, and the gain of the gain controlling circuit 13 is increased, thus keeping the input to an RF amplifying circuit constant. |
