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TK-8100
27
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 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
components, and the resulting signal is goes the antenna ter-
minal.
RF
AMP
RF
AMP
RF
AMP
Q500
Q502
POWER
MODULE
IC502
Q501
DC
AMP
IC203
ANT
SW
D602
D604
D605
LPF
ANT
POWER
DET
D606
D607
IC501
APC
CONTROL
D409
PC
IC161
3pin
+B
Vg
Q411
RF AMP
2SC5108
(Y)F
Q500
RF AMP
2SC5108
(Y)F
Q501
RF AMP
2SC3357
-A
Q502
RF AMP
2SC3357
-A
IC502
ANT
POWER AMP
RA30H3340M
IC161
Q406
D/A
CONVERTER
M62363FP
X401
TCXO
16.8MHz
VCO
2SK508NV
(K52)
IC401
PLL
MB15A02
Q410
BUFFER
2SC5108
(Y)F
Q404
RF AMP
2SC4649
(N,P)
IC203
BUFFER
NJM2902V
IC101
IC161
MIC KEY
INPUT
CPU
30622MAA
-B96GU
D/A
CONVERTER
M62363FP
IC161
D/A
CONVERTER
M62363FP
IC203
SUM AMP
NJM2902V
IC202
IC201
MIC
MIC/IDC
NJM2100V
Splatter
FILTER
NJM2904V
Fig. 9 APC circuit /
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CIRCUIT DESCRIPTION /
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■
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.
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