Kenwood TK-7100 Service Manual page 19

■ 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
MIC/IDC
NJM2100V
NJM2904V
MIC KEY
30622MAA
INPUT
IC161 Q406
D/A VCO
CONVERTER 2SK508NV
M62363FP (K52)
X401 IC401
TCXO PLL
16.8MHz MB15A02
D409
IC161
CIRCUIT DESCRIPTION
Q35
8T
SW
Q36
SW
8TC
LD
IC401
PLL
PLL lock
: LD "H"
IC202 IC203
Splatter
SUM AMP
FILTER CONVERTER
NJM2902V
IC161
IC101
CPU D/A
CONVERTER
-B86GP M62363FP
Q410 IC402
1/2
BUFFER
DIVIDER
2SC5108
UPB1509GV
(Y)
Q404
RF AMP
2SC4649
(N,P)
Fig. 8 Transmitter system
Q501 Q502
RF RF
AMP AMP
IC203
PC
DC
AMP
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 Q501 and Q502. The amplified signal goes to the
power amplifier (IC502) through a low-pass filter. The low-
pass filter removes unwanted high-frequency harmonic com-
ponents, and the resulting signal is goes the antenna termi-
nal.
■ APC Circuit
The automatic transmission power control (APC) circuit
detects the power amplifier (IC502) 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 IC502
and stabilizes transmission output.
The APC circuit is configured to protect over current of
IC502 due to fluctuations of the load at the antenna end and
to stabilize transmission output at voltage and temperature
variations.
IC161
IC203
D/A
BUFFER
NJM2902V
M62363FP
Q411 Q501
RF AMP
RF AMP
2SC4649
2SC3357
(N,P)
IC502 D602~D604
POWER
ANT
MODULE SW
Vg
+B
D606
D607
IC501
APC
CONTROL
TK-7100
Q502 IC502
RF AMP POWER AMP
2SC3357 RA30H1317M-31
ANT
LPF
POWER
DET
ANT
19