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R366
C928
FI3
C926
R885
R352
C460
R414
R400
C491
C470
R351
AM DEMODULATOR CIRCUITS
• DEMODULATOR CIRCUITS (Right band)
NOISE FILTER
X3
180K
R376
C454
R397
C476
R375
AGC voltage to the 1st IF amplifier (Q75)
R415
IF IC (IC18)
1
OSCI
N
2
OSCOUT
3
MIXOUT
4
VCC
5
IFIN
6
DEC
7
FILOUT
8
FILI
N
9
AFOUT
10
QUA
D
11
IF
O
U
T
12
RSSI
13
N-DET
14
N-REC
15
GND
16
MIXI
N
R383
C487
D95
1st IF signal from
the 1st IF amplifier(Q75)
45.9 MHz 2nd LO signal
from the PLL IC (IC14)
C478
C495
C450
R372
C480
C475
D93
R374
R374
C486
D96
R359
C927
R402
C458
0.01
C471
C477
R389
R388
D94
FI4
Q63
1
2
3
4
5
6
R385
C929
R358
Q67
1
2
3
4
5
6
R_R5
R_R5
R_R5
2nd IF FILTERS
R_RSSI
R_SQL
QUADRATURE DETECTOR
AM-demodulated AF signals
to the AF circuits
FM-demodulatedAF signals
from the D/A converter (IC8)
FM-demodulated AF signals
to the AF circuits
RF CIRCUITS
<Right band>
• 118−174 MHz
The received signals from the antenna connector ANT-1
(J1) are passed through two LPFs (L101, 104, 108, C342,
346; L88, 92, 96, C318, 326, 330), then applied to the
RF amplifier (Q37) via TX/RX switch (D59). The amplified
signals are passed through the attenuator (D70) and tuned
BPF (D54, 58), before being applied to another RF amplifi er
(Q32). The amplified signals are applied to the 1st mixer
(IC20) via the another tuned BPF (D40, 43) and RX switch
(D35).
• 375−550 MHz
The received signals from the antenna connector (J1) are
passed through the LPF (L101, 104, 108, C342, 346) and
HPF (L77, 80, C296, 297, 303, 308), then applied to the
RF amplifier (Q28) via TX/RX switch (D53, 61, 62). The
amplified signals are passed through the attenuator (D30)
and tuned BPF (D18, 20, 23, 26), before being applied
to another RF amplifier (Q19). The amplified signals are
applied to the 1st mixer (IC20) via the another tuned BPF
(D10, 12, 14, 16) and RX switch (D7).
• 810−1000 MHz
The received signals from the ANT-1 (J1) are passed
through the HPF (L102, 105, 107, 110, C337, 339, 340,
343, 347, 349) and RX switch (D22), then applied to the RF
amplifier (Q23). The amplified signals are passed through
the attenuator (R39, 40, 51), and applied to the another RF
amplifi er (Q18) to be amplifi ed again. The amplifi ed signals
are then passed through another attenuator (R14) and RX
switch (D9) before being applied to the 1st mixer (IC20).
1ST IF CIRCUITS
RX signals from the RF circuits are converted into the 46.35
MHz 1st IF signal by being mixed with LO signals from the
right band VCO (Q72, D89, 90; Q73, D87, 91, 92).
The converted IF signal from the 1st mixer (IC20) is passed
through the IF fi lter (IF6) to be fi ltered. The fi ltered IF signal is
applied to the 1st IF amplifi er (Q75) via the limiter (D100). The
amplifi ed 1st IF signal is applied to the IF IC (IC18, pin 16)
2ND IF AND DEMODULATOR CIRCUITS
IC15 is an IF IC which contains 2nd mixer, limiter amplifi er,
noise amplifi er, quadrature detector and RSSI circuit, etc. in
its package.
The 1st IF signal from the 1st IF amplifi er (Q75) is converted
into the 450 kHz 2nd IF signal by being mixed with tripled
reference frequency signal (45.9 MHz) from the PLL IC (IC14)
via the tripler (Q52). The converted 2nd IF signal is output
from pin 3, and passed through the ceramic filter (FI3 for
narrow mode, FI4 for wide mode) to remove sideband noise,
then applied to the IF IC from pin 5 again.
• FM DEMODULATOR
The fi ltered 2nd IF signal from pin 5 is amplifi ed at the limiter
amplifier, and FM-demodulated at the quadrature detector
circuit (X3). The demodulated AF signals are output from pin
9 and routed to the AF circuits via two AF switches (IC12
and IC16).
• AM DEMODULATOR CIRCUITS
In the AM mode, the 2nd IF signal from the FI3 is applied to
the AM-demodulator circuit (Q63, Q67). The demodulated
AF signals are routed to the AF circuits via two AF switches
(IC12 and IC16).