The first IF signal is amplified by Q113 and then enters IC102 (TA31136FN), where the
signal is mixed again with the second local oscillator signal (50.4MHz) to become a
450KHz second IF signal. The second IF signal is then fed through a ceramic filter (N:
CF202; W: CF203) to eliminate unwanted signal. The resulting signal then is detected by
IC102 and output from Pin 9 as an AF signal.
2.4 AF Amplifier
The audio signal obtained from IC102 is amplified and filted by IC402 before being
amplified by IC401 (the received signalling inputted into CPU for decode). The processed
signalling passes through Q405 (AF MUTE) and is amplified by IC405. The amplified
signal is fed to K301 (volume control) and Q511 (SP MUTE) on the front panel before
entering AF AMP (IC511). The outputted AF signal drives the Speaker.
2.4 Squelch
The output AF signal from IC102 passes through IC102 Pin8 and is amplified by IC102
again, then is filted and rectified to produce an ASQ level. The ASQ level is comparaed
with the existing reference level in CPU (IC502) to genereate a level to control AF MUTE
and SP MUTE, which determines whether to output sounds from speaker by controlling
Q405 and Q511.
3. Transmitter Circuit
The transmitter circuit is composed of MIC circuit, modulation circuit, RFdirver, final power
amplification circuit and APC circuit.
Fig 2 Transmitter Circuit
3.1 MIC and modulation circuit
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