4 - 3
2ND IF AND DEMODULATOR CIRCUITS
(MAIN UNIT)
<A BAND>
The 1st IF signal from the 1st IF AMP (Q100) is applied to
the IF IC (IC100). The applied 1st IF signal is mixed with
the 61.2 MHz 2nd LO signal (generated by X450, buffered
by Q450) at the internal 2nd mixer, to be converted into the
2nd IF signal. The converted 2nd IF signal is output from pin
3, then passed through the 2nd IF filter (FI100) via IF SWs
(D102, 103).
• FM MODE
The filtered 2nd IF signal is backed to the IF IC from
pin 5, and saturation-amplified by the internal limit AMP.
The amplified 2nd IF signal is FM-demodulated by the
discriminator (X100), and the recovered AF signals (RX
AF signals) are output from pin 9, then applied to the AF
circuits via the AF mute SW (IC500, pins 8, 9).
• AM MODE
The filtered 2nd IF signal is amplified by 2nd IF AMP (Q103),
then applied to the AM demodulator circuit (Q104, 105,
D105) to be recovered to the AF signals. The demodulated
AF signals are applied to the AF circuits.
<B BAND>
The 1st IF signal from the 1st IF AMP (Q200) is applied to
the IF IC (IC200). The applied 1st IF signal is mixed with
45.9 MHz 2nd LO signal (generated by X450, tripled by
Q451) at the internal 2nd mixer, to be converted into the
450 kHz 2nd IF signal. The converted 2nd IF signal is output
from pin 3, then passed through one of the 2nd IF filters.
The 2nd IF signal is passed through FI200 in FM/AM mode,
and passed through FI1201 in FM-N mode.
• FM/FM-N/DV MODE
The filtered 2nd IF signal is backed to the IF IC from pin
5, then saturation-amplified by the internal limit AMP.
The amplified 2nd IF signal is FM-demodulated by the
discriminator (X200), and the recovered AF signals (RX
AF signals) are output from pin 9, then applied to the AF
circuits via the AF mute SW (IC500, pins 4, 3).
• AM MODE
The filtered 2nd IF signal is amplified by another 2nd
IF AMP (Q202), then applied to the AM demodulator
circuit (Q203, 204, D205) to be AM-demodulated. The
demodulated AF signals are applied to the AF circuits.
C113
X100
C124
R107
R114
R117
R108
C111
C126
C123
IC100
1
OSCIN
2
OSCOUT
3
MIXOUT
4
VCC
5
IFIN
6
DEC
7
FILOUT
8
FILIN
9
AFOUT
10
QUAD
11
IFOUT
12
RSSI
13
N-DET
14
N-REC
15
GND
16
MIXIN
C138
C116
C114
FI100
I
O
R116
R119
D102
C136
R111
C125
C117
0
C
D103
R106
L101
C122
R115
C108
C137
R112
C115
4
5
R113
C121
R118
C109
C112
R105
C143
C134
47K
R124
R131
R120
C133
R123
C130
.1
131
R121
R122
Q104
1
2
3
4
5
6
C142
R133
R127
R125
C129
R130
C135
D104
R126
R132
D105
100
C128
C127
Q103
1
2
3
4
5
6
1
144
AM demodulator
2nd IF AMP
for AM mode
3RD IF CIRCUIT (MAIN UNIT)
(FOR A BAND, WFM MODE ONLY)
The 2nd IF signal from the 2nd IF AMP (Q100) is applied to
the IF IC.
The applied 2nd IF signal is mixed with the 15.3 MHz 3rd
LO signal (generated by X450, buffered by Q450), to be
converted into the 1.95 MHz 3rd IF signal by the internal 3rd
mixer. The converted 3rd IF signal is output from pin 3, and
passed through the IF SWs (D102, 103), then backed to the
IF IC (bypassing FI100). The 3rd IF signal is FM-demodulated
by the discriminator (X100), and the recovered AF signals
(RX AF signals) are output from pin 9, then applied to the AF
circuits via the AF mute SW (IC500, pins 8, 9).
C237
R227
IC200
1
OSCIN
2
OSCOUT
3
M IXOUT
4
VCC
5
IFIN
6
DEC
7
FILOUT
8
FILIN
9
AFOUT
10
QUAD
11
IFOUT
12
R SSI
13
N-DET
14
N -REC
15
GND
16
MIXIN
EP200
C236
C213
C212
R231
R210
X200
C220
C211
R214
R209
C206
C215
C221
C207
0.1
C241
C216
FI200
I
O
C208
C222
C214
D202
R205
C238
FI201
I
O
C224
R215
C223
R216
R206
C225
D203
R218
R220
R221
C230
K
5
Q202
1
2
3
4
5
6
C232
R233
R217
C233
R224
Q203
1
2
3
4
5
6
D205
R234
1
62
R306
100
C229
D204
1
C261
0.1
234
R219
R223
C226
C227
C228
C231
R225
R305
AM demodulator
2nd IF AMP
for AM mode
• 2ND IF AND FM DEMODULATOR CIRCUITS (A BAND)
• 2ND IF AND FM DEMODULATOR CIRCUIT (B BAND)
• AM DEMODULATOR CIRCUIT (A BAND)
• AM DEMODULATOR CIRCUIT (B BAND)
