TM-V71A/V71E
5
2-5. Audio Circuit
The detected band A audio signal is amplifi ed by Q810
and de-emphasized by Q806. The band B audio signal is
amplified by Q811 and de-emphasized by Q807. One of
these audio signals is selected with a cross point switch
(IC806). The signal passes through the electronic volume
ANT
SW
D/A
AIP
SW
D164,165
D187,189
LPF
RF AMP
Q363
RF AMP
Q362
IF AMP
Q495
X486
45.505MHz
MIXER
Q361
MCF
XF486
CF
Wide
IC576
Q400
BPF
D378,379
L377
BPF
D375,376
L375
BPF
D370,371
L370
BPF
D364,365
L366
BPF
D367,368
L368
CF
Narrow
IC667
MPU
IC918
FM IC
IC486
1st Local OSC
Band A
Band B
2nd Local OSC
Band A
AF
2nd Local OSC
45.05MHz
D/A
AIP
SW
RF AMP
Q408
RF AMP
Q407
IF AMP
Q551
MIXER
Q406
MCF
XF546
CF
Wide
IC576
Q450
BPF
D423,424
L422
BPF
D420,421
L420
BPF
D415,416
L415
BPF
D409,410
L411
BPF
D412,413
L413
CF
Narrow
IC667
MPU
IC918
FM IC
IC546
1st Local OSC
Band B
AF
49.95MHz
TCXO
X66
Tripler
x3
16.8MHz
Q547
Fig. 3 Band A and Band B UHF receiver circuit
Q807
Q811
IC805
1/2
IC805
1/2
DE-EMPHASIS B
Q806
Q804
Q803
Q810
DE-EMPHASIS A
IC918
MPU
CTCSS Filter AMP
BEEP
DTMF
IC806
Cross
Point
SW
IC804
E VR
MUTE1
MUTE2
ATT
IC801
AF AMP
J801
(SP1)
J802
(SP2)
IC666
Multi
SW
IC486
FM IC (A)
IC546
FM IC (B)
Q816
Fig. 4 Audio circuit
(IC804), is amplifi ed by the AF amplifi er (IC801), and is then
fed to the speaker or the external speaker jack.
CTCSS and DCS signals that pass through the filter
circuit (IC805) go to the MPU (IC918) for CTCSS and DCS
decoding.
3. Transmitter System
3-1. Modulation Circuit
The audio modulation input from the microphone is
amplifi ed by IC802. After the DTMF signal and 1750Hz tone
signal generated by the MPU are switched with IC806, they
are mixed by IC803. After the signal amplified by IC802
is switched by IC806, it is amplifier by IC803. The signal
is then pre-emphasized by Q805 and Q808, and its level
is adjusted by IC804. The resulting signal goes to each of
the band A and band B VCOs as a modulation signal. The
TONE/ DCS signal generated by the MPU is fed to IC803.
The signal amplifi ed by IC803 is distributed and the level is
adjusted by IC804. The modulating signal goes to each of
the band A and band B VCOs and the reference oscillation
circuit.
CIRCUIT DESCRIPTION