RCA BR200D-U1 Service Manual page 26

decrease, finally the output power of transmitter will decrease or vice versa. Thus, the output power of
transmitter will keep stable under any different working condition.
MCU can set the power by changing the voltage input to IC100B.
Audio Signal Processing of Transmitter
The audio signal processing circuit of Transmitter consists of IC601 and IC609. Voice signals from
MIC are sent to VCO for modulation together with CTCSS/DCS after amplification, limitation and filtering.
IC609 is a bais band processor.
AGC circuit consists of D601, D602 and Q602,Q603. The signal amplitude is reduced to ensure no
distortion in case of oversized MIC signal.
Q601, the power switch of voice processing circuit, controlled by MCU, will give power supply to IC601
only during transmission.
J501 is the socket for external MIC, and the internal MIC will disconnect automatically when using
external MIC, but the internal PTT is still effective.
5.4 PLL Frequency Synthesizer
The DR-6000(7000) adopts PLL frequency synthesizer.
Figure 6 Schematic Diagram for Audit Circuit of Receiver
Figure 7 Schematic Diagram for Frequency Synthesizer
BR200D-U1/BR300D-U1 Service Manual
26