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3.
Loss of lock detector
If the pulse signal appears on the PLD pin, a lockout occurs,The DC voltage obtained from C671, R623
and D601 lowers the input voltage of the microprocessor. The microprocessor detects this condition
after the launch is disabled, ignoring the PTT switch input signal.
4.
Transmitter system
1)
Microphone amplifier
The signal from the microphone passes through the U201. When the encoder is DTMF, the input signal of
the microphone is closed by U201. The signal is modulated by audio processing (U204), and then sent to VCO
modulation input.
The signal from the VCO is amplified by the pre-driver amplifier (Q503) and the driver amplifier (Q502)
to 50mW.The output of the driver amplifier is amplified by the RF power amplifier (Q501) to 4.0W (1W at
low power). The RF power amplifier is composed of two MOSFETs. The output of the RF power amplifier is
connected by a harmonic filter (LPF) and an antenna switch ( D501) and sent to the antenna terminal.
as picture 5 PLL Circuit
as picture 6 Microphone amplifier
2)
Drive and terminal amplifier
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