Kenwood TM-D700A Service Manual page 9

TM-D700A/E
CIRCUIT DESCRIPTION
3. Transmitter system
3-1.Modulation Circuit
The audio modulation input from the microphone is
amplified by |1C801. The 1200bps packet signal generated by
the X52-331 goes to iIC801. The DTMF signal and 1750Hz
tone signal (E type only) generated by the CPU are also mixed
by IC801. The modulation signal from the DATA terminal is
switched by IC803. It is directed to C801 in 1200bps mode and
to 1C802 in 9600bps mode. The signal amplified by IC801 is
pre-emphasized by Q801 and Q802, and its level is adjusted
PRE-EMPHASIS
AF AMP
MIC AMP
C801
NJM2100V4
MIC
[}———
X§2-331
1200bps DTMF 1750
TONE AMP
by IC804, and the resulting signal goes to each of the VHF and
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 C802 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.
M62364FP
IC804
'
AMP
IC300
YUM2904V;
sw
IC802
CPU TA75501F
Ba
PKD OF
B
1200bps
IC803
BU4066
BCFV
TONE/CTCSS/DCS
Fig.9 Modulation curcuit
3-2.Transmitter circuit
The VHF VCO output is amplified by 3-stage amplifier, RF
amplifier (Q6) and driver amplifier (Q8, QQ). It is amplified to the
final output by the power module. The signal passes through
antenna switch (D14, D15) and low-pass filter and is fed to the
antenna.
ANT
VHF VCO RF AMP DRIVER DRIVER POWER AMP _ Y
Ic2 as ~Le
KCH38
2802954
M67746
|
;
AIT
UHF VCO POWER AMP LPF HPF
IC302 : i —~
Fig.10 Transmitter curcuit