Kenwood TK-8102H Service Manual page 13

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 passes through
the transmission/reception selection diode (D19) and ampli-
fied by Q39, Q23, Q800 and Q801. The amplified signal
goes to the final amplifier (Q101) through a low-pass filter.
The low-pass filter removes unwanted high-frequency har-
monic components, and the resulting signal is goes the an-
tenna terminal.
APC Circuit
The automatic transmission power control (APC) circuit
detects part of a final amplifier (Q101) output with a diode
(D805, D806) and applies a voltage to IC800. IC800 com-
pares the APC control voltage (PC) generated by the D/A
converter (IC3) and DC amplifier (IC4) with the detection
output voltage. IC800 generates the voltage to control
Q800, Q801 and Q101 and stabilizes transmission output.
The APC circuit is configured to protect over current of
Q800, Q801 and Q101 due to fluctuations of the load at the
antenna end and to stabilize transmission output at voltage
and temperature variations.
Q39 Q23 Q800
PRE
RF DRIVE
D19 DRIVE
AMP
AMP1
AMP
IC4
PC
DC
IC3
AMP
3pin
Fig. 9 APC circuit
MIC IC21(1/2) IC22
Splatter
MIC/IDC
FILTER
NJM2100V
NJM2904V
IC6
MIC KEY CPU
INPUT 784214GC
IC3 Q11
D/A VCO
CONVERTER 2SK508NV
M62363FP (K52)
X1 IC1
TCXO PLL
16.8MHz MB15A02
CIRCUIT DESCRIPTION
Q801 Q101 D801~804
DRIVE FINAL ANT
SW
AMP2 AMP
D805
D806
POWER
IC800
APC
CONTROL
IC3
IC4
D/A
SUM AMP
CONVERTER
NJM2902V
M62363FP
IC3
D/A
CONVERTER
M62363FP
Q15 Q20
BUFFER RF
2SC5108 2SC5108
(Y) (Y)
Q3
RF AMP
2SC4649
(N,P)
Fig. 8 Transmitter system
Control Circuit
The CPU carries out the following tasks:
1) Controls the WIDE, NARROW, TX/RX outputs.
2) Adjusts the AF signal level of the AF filter (IC10) and turns
the filter select compounder on or off.
3) Controls the DTMF decoder (IC9).
4) Controls the display unit.
5) Controls the PLL (IC1).
6) Controls the D/A converter (IC3) and adjusts the volume,
modulation and transmission power.
DTMDAT
IC9
DTMCLK
DTMF
DTMSTD
DECO.
Fig. 10 Control circuit
Memory Circuit
The transceiver has an 8k-bit EEPROM (IC7). The
EEPROM contains adjustment data. The CPU (IC6) controls
the EEPROM through three serial data lines.
ANT
IC6
CPU
LPF
Fig. 11 Memory circuit
DET
IC4
BUFFER
NJM2902V
Q39 Q23
RF AMP PRE
2SC5110 DRIVE AMP
2SC3356(R24)
(O)
TK-8102H
CNTCK
CNTDT
DAST
IC6
PLLE
CPU
DT
CK
EEPCK
EEPDT
IC7
EEPROM
EEPWP
Q800 Q801 IC101
DRIVE DRIVE
FINAL AMP
AMP 1 AMP 2
2SK3478-22
2SK2596 2SK3075
IC3
D/A
converter
IC1
PLL
ANT
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