Alinco DJ-100, Руководство по обслуживанию

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DJ-100
4
QUAD
AFOUT
C580
T500
R551
R528
Q507
Q509
U502
FM SYSTEM
IFOUT
5R
P60 (U206)
L:Wide
H:Narrow
AF OUT
From MPU
SP MUTE
T500
2nd local OSC
CF500
450kHz
C654
R560
R591
(38.40MHz)
R549
Quadrature
detector
10
9
11 12 13 14 15 16
8 7 6 5 4 3 2 1
RSSI
Local
OSC
MIX
Rectifier
Noise
comp
IF AMP
LPF
Inverter
AMP
AMP
Noise
Buffer
C655
5R
P61
MPU
P00
P04
RSSI
SQ
U206
1st IF input
(38.85MHz)
AF OUT
SW
U200
SP
AF PA
LS200
U205
AQUA
U203B
J200
VOL
AMP
Q202,Q206
FM IC
U502
SW
CIRCUIT DESCRIPTION
Fig.3
3-1-5.
Squelch and Mute Circuit
A noise component is obtained by passing FM
detection output (FM IC pin 9) through an operational
amplifier in the FM IC and band-pass filter consisting of
R549, R560, R591, C654, C655. The noise component is
rectified in the FM IC to produce a DC voltage, which is
output from the N-REC terminal (pin 14) of the FM IC as
squelch voltage.
The squelch voltage enters the SQ terminal (pin 50) of
the MPU (U206) and is compared with the reference
voltage preset in the MPU to control audio signal
ON/OFF.
To output sounds from the speaker, U206 sends a high
signal to the P61 line and turns U205 on through Q202
and Q206. (See Fig.4)
3-1-6. S Meter Circuit
The S meter voltage is output from the RSSI terminal
(pin 12) of the FM IC (U503) and input to the SM terminal
(pin 54) of the MPU. Then the voltage is converted from
analog to digital in the MPU to control the S meter display
on the LCD. (See Fig.4)
Fig.4
3-2. AF signal system
3-2-1. Audio amplifier circuit
The demodulated signal from U501 goes to Audio
processor through U200 (AF filtered, low-pass filtered,
high-pass
filtered, De-Scrambler, Expander, and
de-emphasized).
The signal then goes through an AF amplifier U203B
(2/2), an AF volume control (W200), and is routed to an
audio power amplifier (U205), where it is amplified and
output to the internal speaker. (See Fig.5)
3-2-2. Receive Signalling
3-2-2-1 Low-speed data
（
CTCSS/DCS
）
300 Hz and higher audio frequencies of the output signal
from IF IC are cut by IC (U502) within a low-pass filter.
U200 determines whether the CTCSS or DCS matches the