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4-3-3 REFERENCE OSCILLATOR CONTROL
CIRCUIT (LOGIC AND MAIN UNITS)
The reference oscillator control circuit changes the refer-
ence frequency when using digital voice function.
When digital voice signals output from the optional digital
voice unit, the “REFMOD” signal outputs from it via the J4
(pin 4) at the same time. The “REFMOD” signal is applied to
the amplifier (IC521, pin 3), and passes through the CTCSS
switch (IC524, pins 6 and 1). The signal is applied to the D/A
convertor (MAIN unit; IC5, pin 13) via the “CTCSS” line. The
output signal from the D/A convertor (MAIN unit; IC5, pin 14)
is applied to the reference oscillator (MAIN unit; X1) to con-
trol the reference frequency while transmitting digital signals
as “DTC” line.
4-4 POWER SUPPLY CIRCUITS
VOLTAGE LINES
Description
The 13.8 V voltage from the connected DC
power supply.
The same voltage as the HV line which is con-
trolled by the HVSW circuit (Q28, Q30, Q31).
When the [POWER] switch (LOGIC unit; S1) is
pushed, the CPU (LOGIC unit; IC1, pin 40) out-
puts the “PWRON” control signal to the power
switching circuit to turn the circuit ON.
Common 5 V for the CPU (LOGIC unit; IC1)
converted from the HV line by the C5V regulator
circuit (IC8). The circuit outputs the voltage
regardless of the power ON/OFF condition.
Common 8 V converted from the SWHV line by
the +8V regulator circuit (IC7).
Common 5 V converted from the +8V line by the
+5V regulator circuit (Q21, Q22).
Transmit 8 V controlled by the T8 regulator cir-
cuit (Q14, Q15) using the “TXC” signal from the
I/O expander IC (IC2, pin 6). The voltage is con-
verted from the +8V line at the regulator circuit.
Receive 5 V controlled by the R5 regulator cir-
cuit (Q25) using the “RXC” signal from the I/O
expander IC (IC2, pin 5). The voltage is con-
verted from the +5 V line at the regulator circuit.
Line
HV
SWHV
C5V
+8V
+5V
T8
R5V
Pin
number
2
3
10
11
14
15
22
23
Port
name
T3
SQLATT
FC
SQLIN
DTC
MOD
T2
T1
Description
Outputs RF tracking voltage while
receiving.
Outputs attenuator control signal.
Outputs reference frequency control
voltage.
Outputs squelch control signal to
adjust threshold level.
Outputs DTCS slope correction signal.
Outputs transmitting deviation control
signal.
Outputs RF tracking voltage while
receiving.
• Outputs RF tracking voltage while
receiving.
• Outputs transmitting power control
signal while transmitting.
4-5 PORT ALLOCATIONS
4-5-1 D/A CONVERTER IC (MAIN UNIT; IC5)
Pin
number
4
5
6
11
14
Port
name
AFMUTE
RXC
TXC
W/N
SHIFT
Description
Outputs AF mute control signal.
High: While muting.
Outputs R5 regulator (Q25) control
signal.
Low: While receiving.
Outputs T8 regulator (Q14 and Q15)
control signal.
High: While transmitting.
Outputs 2nd IF filter select signal
([W/N] version ONLY).
High: While wide passband width
(±5.0 kHz) is selected (FI1 is
selected).
Low: While narrow passband width
(±2.5 kHz) is selected (FI2 is
selected).
Outputs VCO regualtor (Q1, Q3, Q5,
Q8, D1) control signal.
Low: While transmitting.
High: While receiving.
4-5-2 EXPANDER IC (MAIN UNIT; IC2)