RADIO LOWWNOISE RECEIVING DEVICE

摘要

PURPOSE:To avoid the saturation of the intermediate frequency amplifier by providing the level monitor circuit to the low-noise receiving device. CONSTITUTION:The signal received through antenna 1 is applied to mixer 3 via circulator 11 and low-noise amplifier 12. The signal sent from mixer 3 is amplified and filtered through intermediate frequency preamplifier 5, intermediate frequency filter 6 and main intermediate frequency amplifier 7 respectively. The output of AGC circuit controlling the gain of amplifier 7 is applied also to reception input field level monitor circuit 9. Circuit 9 delivers the control signal to break the power source of amplifier 12 when the level is high to avoid the saturation of amplifier 5 and 7. While amplifier 12 is actuated to secure the low-noise reception when the level is low.