Kenwood TKR-D710 Service Manual page 13

volume control circuit. The 2nd electronic volume control
circuit adjusts the modulating signal and is fed to IC606.
IC603 is an inverting amplifi er for inverting the amplifi -
cation of the modulating signal. The output of IC603 and
the charge pump output of IC602 (Transmitter modulation
16.8MHz PLL IC) are synthesized by IC604 and is fed to
VCXO (X600).
IC606 is a non-inverting amplifi er. The output of the 2nd
electronic volume control circuit is amplifi ed by IC606 and is
fed to the transmitter main PLL circuit.
AMP
X58-5200-10
IC606
TX VCO
/PLL
AMP AMP
X600
IC604 IC603
OSC
16.8MHz
Fig. 5 Modulation level adjustment circuit
2-5. Front-end circuit
The front-end circuit consists of LPF , L111, L112, L114,
and L115 coils, former BPF tuning Variable Capacitance
Diodes (D105, D106, D107 and D108), RF amplifier Q101
(LNA), L100, L101, L103, and L104 coils, and latter BPF
tuning Variable Capacitance Diodes (D100, D101, D103 and
D104). The BPF covers frequency ranges 136 to 174MHz.
The LPF , former and latter BPF attenuate the unwanted
signals receiving from RX antenna (CN101) and only the de-
sired signals transmit to the 1st-mixer.
IF AGC AMP
Q300
RSSI
450kHz
CN802
CIRCUIT DESCRIPTION
CN800
VREF
IC605
MO
EVOL
IC804
MOD
MB
Buffer
IC401(A/2)
Diff AMP
IC401(B/2)
IC405
SW
AMP
IC409(A/2,B/2)
IF AMP
IC400
Fig. 8 IF circuit
BPF
136~
174MHz
EVOL
Buffer
IC804
IC100
Fig. 6 Front-end circuit
2-6. 1st-Mixer circuit
The signal passing the front-end circuit is heterodyned
with the fi rst local oscillator signal from the PLL frequency
synthesizer circuit at the first mixer (IC300) to become a
58.05 MHz fi rst intermediate frequency (IF) signal.
136~174MHz
Fig. 7 1st-Mixer circuit
2-7. IF circuit
The fi rst IF signal is amplifi ed by the IF Post Amp (Q301)
and passed through a four-pole monolithic crystal filter
(XF300) to reject adjacent channel signals. The fi ltered fi rst
IF signal is amplified by the IF AGC amplifier (Q300) and
then applied to the IF system IC (IC403). The IF system IC
MCF POST AMP
XF300 Q301
58.05MHz
RSSI
CF400
IF2
CF402
IC406 IC408 IC407
SW SW SW
CF403
CF401
IF AMP
IC404
TKR-D710
LNA AMP
BPF LPF
Q101
Buffer
IC101
Mixer
IC300
IF1
58.05MHz
1st Local
194.05~232.05MHz
IF1
2nd Lo
IF IC
57.6MHz
IC403
RX ANT
CN101
136~
174MHz
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