Kenwood TK-863G Service Manual page 20

TK-863G
IC3 : PLL IC
PLL
DATA
16.8MHz
Unlock Circuit
During reception, the 8RC signal goes high, the 8TC sig-
nal goes low, and Q16 turns on. Q18 turns on and a voltage
is applied to the collector (8R). During transmission, the
8RC signal goes low, the 8TC signal goes high and Q29
turns on. Q28 turns on and a voltage is applied to 8T.
The CPU in the TX-RX unit (B/2) monitors the PLL (IC3)
LD signal directly. When the PLL is unlocked during trans-
mission, the PLL LD signal goes low. The CPU detects this
signal and makes the 8TC signal low. When the 8TC signal
goes low, no voltage is applied to 8T, and no signal is trans-
mitted.
8R
LD
IC3 IC502
PLL CPU
PLL lock
: LD "H"
TX-RX UNIT (B/2)
Fig. 7 Unlock circuit
MIC IC507(1/2) IC508
AF AMP,
AF AMP
IDC, LPF
NJM2904V
TC35453F
IC502
CPU
MIC KEY
30622M
INPUT
4A-410GP
20
CIRCUIT DESCRIPTION
10kHz/12.5kHz
1/N
Phase Charge
comparator pump
REF
OSC
1/M
10kHz/12.5kHz
8C
Q18 Q28
8T
SW SW
Q16 Q29
SW SW
8RC
8TC
IC9
SHIFT
REG.
VCO
IC6 Q103
D/A VCO
CONVERTER 2SK508NV
M62363FP (K52)
IC1 X1 IC3
SUM AMP VCXO PLL
TA75S01F 16.8MHz MB15A02
Fig. 8 Transmitter system
HPF
PLL/VCO
Q103
TX VCO
LPF
D102,104
Q101
RX VCO
D101,103
Fig. 6 PLL circuit
Transmitter System
Outline
The transmitter circuit produces and amplifies the de-
sired frequency directly. It FM-modulates the carrier signal
by means of a varicap diode
Power Amplifier Circuit
The transmit output signal from the VCO is amplified to a
specified level of the power module (IC400) by the drive
block (Q22, Q25 and Q27). The amplified signal passes
through the transmission/reception selection diode (D16)
and goes to a low-pass filter. The low-pass filter removes
unwanted high-frequency harmonic components, and the
resulting signal is goes the antenna terminal.
Q14
Q106
BUFFER
BUFFER
2SC4226 2SC5110
2SC4093
(R24) (O)
Q9
X2 MULTIPLY
2SC4226
(R24)
Q106
Q9
BUFF
X2 multiply
AMP
Q102,
104,105
T/R SW
Q22 Q25 Q27
RF AMP RF AMP RF AMP
2SC3357 2SC2954
ANT
IC400
POWER AMP
S-AU27AM(K3)