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• TX AF CIRCUITS
• MODULATION CIRCUITS
• TX AMPLIFIERS APC CIRCUIT
5 - 3
5-2 TRANSMITTER CIRCUITS
MIC AMPLIFIER (FRONT UNIT)
Audio signals from the connected microphone are applied to
the MIC AMP (IC5) via the microphone connector (J1). The
amplifi ed MIC signals are applied to the MAIN UNIT.
TX AF CIRCUITS
The MIC signals from the FRONT UNIT are passed through
the D/A converter (as a MIC gain controller; IC18) for level
adjustment, and applied to the limiter AMP which is also
rolled to the pre-emphasis circuit (IC16).
MIC MUTE SWITCH
The pre-emphasized MIC signals are passed through the
MIC mute SW (IC14).
While receiving, the MIC mute SW (IC14) cuts the MIC line
off, and is controlled by “MMUT” signal from the expander
(IC17).
SPLATTER FILTER
The MIC signals from the MIC mute SW (IC14) are applied
to the splatter fi lter (IC16).
The splatter filter (IC16) is also used as the AF Summing
AMP for tone signals modulation (CTCSS, 2/5 TONE).
MODULATION CIRCUIT
MIC signals from the splatter filter (IC16) is level-adjusted
(=deviation adjustment) by the D/A converter (IC18), and
applied to the TX VCO (Q13, D16, 31) via modulation mute
SW (IC14) as the modulation signals.
The MIC signals are also applied to the reference frequency
oscillator (X2) as the modulation signals via D/A converter
(IC18) and REF AMP (IC19).
CTCSS/DTCS SIGNALS ENCODING (FRONT UNIT)
The CTCSS/DTCS encoding signals from the CPU (IC1)
“CENC0–CENC2” are passed through the LPF (IC5) for
waveform conversion, and applied to the MAIN UNIT as tone
modulation signals.
2/5 TONE, DTMF ENCODING (FRONT UNIT)
Encoding signal from the CPU (IC1) named “SENC” is
passed through the LPF (IC5), and applied to the MAIN
UNIT as tone modulation signals.
TX AMPLIFIERS
The frequency-modulated signal from the TX VCO is buffer-
amplifi ed by two buffers (Q11 and Q10), and applied to the
drive AMP (Q9) as the TX signal via the LO SW (D14). The
amplifi ed TX signal is applied to the FET HPA module (IC3)
via the LPF, and power-amplifi ed to obtain TX output power
level.
The power-amplified TX signal is passed through the
antenna SW (D3) and LPF as a harmonic filter, then fed to
the antenna.
APC CIRCUIT
A portion of TX signal rectifi ed by D1, D11 and D12 on the
TX line to detect TX power level. The rectified voltage is
applied to the APC AMP (IC2), and the APC AMP controls
the gain of HPA module (IC3) automatically by comparing
the rectifi ed voltage and the power setting voltage "T1."
Splat.
IC16
Limiter
Pre-empha.
IC16
AMP
IC5
HPF
MIC
line
SW
MIC
D/A
IC14
CD4066
IC18
A K2330
MICROPHONE
CONNECTOR
J1
FRONT UNIT
MIC
BAL
To the Reference
frequency oscillator
MODI
MCOT
MCGO
TONE
CDTS
MOD
VRAF
TX VCO
SPIN
REF
OSC
X2
CR-794
TX/RX
SW
D14,D15
Q13,D16,31
FIL
LOOP
PLL
IC
IC4
MB15A02
FM
MOD
D18
BUFF
Q10
BUFF
Q11
IC19
AMP
REF
TX VCO
BAL
15.3 MHz
From the D/A converter
From the MIC line SW
To TX AMPs
LV
LPF
LPF
LP F
LP F
PWR
DET
D11,D12
MUTE
SW
D28
ANT
SW
D3
PWR
AMP
IC
RX circuits
3
APC
AMP
IC2
DRIVE
AMP
Q8
T1
TMUT
136-174 MHz
From TX VCO