Kenwood TK-8100H Service Manual page 17

■ Unlock Circuit
During reception, the 8RC signal goes high, the 8TC signal
goes low, and Q34 turns on. Q33 turns on and a voltage is
applied to the collector (8R). During transmission, the 8RC
signal goes low, the 8TC signal goes high and Q36 turns on.
Q35 turns on and a voltage is applied to 8T.
The CPU in the control unit monitors the PLL (IC401) LD
signal directly. When the PLL is unlocked during transmis-
sion, the PLL LD signal goes low. The CPU detects this sig-
nal and makes the 8TC signal low. When the 8TC signal goes
low, no voltage is applied to 8T, and no signal is transmitted.
8C
Q33
8R
SW
Q34
SW
8RC
IC101
CPU
Fig. 7 Unlock circuit
MIC IC201 IC202
Splatter
MIC/IDC
FILTER
NJM2100V
NJM2904V
IC101
CPU
MIC KEY
30622MAA
INPUT
-B76GP
IC161 Q406
D/A VCO
CONVERTER 2SK508NV
M62363FP (K52)
X401 IC401
TCXO PLL
16.8MHz MB15A02
D409
CIRCUIT DESCRIPTION
Q35
8T
SW
Q36
SW
8TC
LD
IC401
PLL
PLL lock
: LD "H"
IC161
IC203
D/A
SUM AMP
CONVERTER
NJM2902V
M62363FP
IC161
D/A
CONVERTER
M62363FP
Q410 Q411 Q500
BUFFER RF AMP RF AMP
2SC5108 2SC5108 2SC5110
(Y) (Y)
Q404
RF AMP
2SC4649
(N,P)
Fig. 8 Transmitter system
Q500 Q501 Q502
PRE
RF DRIVE
DRIVE
AMP AMP1
AMP
IC501
IC203
PC
DC
IC161
AMP CONTROL
3pin
Fig. 9 APC circuit
Transmitter System
■ Outline
The transmitter circuit produces and amplifies the desired
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 (D409) and ampli-
fied by Q500, Q501, Q502 and Q503. The amplified signal
goes to the final amplifier (Q504) 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 (Q504) output with a diode
(D606, D607) and applies a voltage to IC501. IC501 com-
pares the APC control voltage (PC) generated by the D/A con-
verter (IC161) and DC amplifier (IC203) with the detection
output voltage. IC501 generates the voltage to control Q502,
Q503 and Q504 and stabilizes transmission output.
The APC circuit is configured to protect over current of
Q502, Q503 and Q504 due to fluctuations of the load at the
antenna end and to stabilize transmission output at voltage
and temperature variations.
IC203
BUFFER
NJM2902V
Q501 Q502
PRE DRIVE
DRIVE AMP
AMP 1
(O) 2SC3356(R24) 2SK2596
Q503 Q504 D601~D604
ANT
DRIVE FINAL
AMP2 AMP SW
D606
D607
VR1
APC
TK-8100H
Q503 Q504
DRIVE
FINAL AMP
AMP 2 RD60HUF1
PD55008TR -01
ANT
LPF
POWER
DET
ANT
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