Kenwood TM-V708A Service Manual page 8

TM-V708A
3. Transmitter system
3-1. Modulation Circuit
The audio modulation input from the microphone is
amplified by IC801. The DTMF signal and 1750Hz tone signal
generated by the CPU are also mixed by IC801. The
modulation signal from the DATA terminal is switched by
IC803. It is directed to IC801 in 1200bps mode and to IC802
in 9600bps mode. The signal amplified by IC801 is pre-
emphasized by Q801 and Q802, and its level is adjusted by
IC804, and the resulting signal goes to each of the VHF and
MIC
SW
IC803
PKD BU4066
BCFV
3-2. Transmitter circuit
The VHF VCO output is amplified by 3-stage amplifier, RF
amplifier (Q6) and driver amplifier (Q8, Q9). It is amplified to
the final output by the power module. The signal passes
through antenna switch (D14, D15) and low-pass lifter and is
fed to the antenna.
VHF VCO
UHF VCO
Q304
IC302
2SC5108
KCH28
(Y)
8
CIRCUIT DESCRIPTION
PRE-EMPHASIS
MIC AMP
Q801
IC801
2SC4617
NJM2100V
(S)
DTMF1750
CPU
1200bps
TONE/CTCSS/DCS
Fig. 8 Modulation circuit
RF AMP DRIVER
Q6
IC2 Q8
2SC5108
2SC3357
KCH38
(Y)
Q307
Q309
2SC4093
2SC3357
(R27)
Fig. 9 Transmitter circuit
UHF VCOs as a modulation signal. The TONE/CTCSS/DCS
signal generated by the CPU is fed to IC802 in the same way
as the 9600bps mode signal from the DATA terminal. The
signal amplified by IC802 is distributed and the level is
adjusted. The modulating signal goes to each of the VHF and
UHF VCOs. The signal is amplified by IC300 and modulates
the reference oscillation circuit.
AF AMP
M62364FP
Q802
IC804
2SC4617
(S)
TONE AMP SW
IC803
IC802
BU4066
TA75S01F
BCFV
The UHF VCO output is amplified by 4-stage amplifier, RF
amplifier (Q304) and driver amplifier (Q307, Q309, and Q310).
It is further amplified to the final output by the power module.
The signal passes through antenna switch (D314), low-pass
filter and high-pass filter. Then it is fed to the antenna.
DRIVER
POWER AMP
Q9
M67746
2SC2954
POWER AMP
Q310
M57788MR-24
2SC2954
VHF
VCO
IC2
KCH38
AMP
IC300
NJM2904V
UHF
VCO
IC302
KCH28
ANT
LPF
ANT
LPF HPF