4 - 1
• RF CIRCUITS
• 1ST IF CIRCUITS
• 2ND IF CIRCUITS
• RX AF CIRCUITS
• DIGITAL DEMODULATION CIRCUITS
SECTION 4
CIRCUIT DESCRIPTION
4-1 RECEIVE CIRCUITS
RF CIRCUITS (MAIN UNIT)
The RX signal from the antenna is passed through two LPFs
(L32, L34, C302, C303, C306, C307, C312 and L29, C281,
C285), ANT SW (D24, D25, D31, D33, L36, C313, C315,
C319) and tuned BPF (D32, L43, C353), and then applied to
the RF AMP (Q47).
The amplifi ed signal is passed through the tuned BPF (D27, D29,
D30, L28, L31, L33, C286, C290, C292, C293, C297, C299–
C301, C304, C305), and then applied to the 1st IF circuits.
1ST IF CIRCUITS (MAIN UNIT)
The RX signal from the RF circuits is applied to the 1st IF
mixer (Q46), and mixed with the 1st LO signal from the VCO
(Q27, D10–D12), resulting in the 46.35 MHz 1st IF signal.
The 1st IF signal is passed through the 1st IF fi lter (FI3) and
limiter (D23), and then applied to the 1st IF AMP (Q44). The
amplifi ed signal is passed through another limiter (D22), and
then applied to the 2nd IF circuits.
2ND IF CIRCUITS (MAIN UNIT)
The 1st IF signal from the 1st IF circuits is applied to the IF IC
(IC13, pin 16). The IF IC contains the 2nd mixer, 2nd IF AMP,
detector, and so on, in its package.
The 1st IF signal is mixed with the 2nd LO signal from the
reference frequency oscillator (TCXO: X1), resulting in the
450 kHz 2nd IF signal. The 2nd IF signal is passed through
the 2nd IF fi lter (FI1: for DV/FM-N mode, FI2: for FM mode)
to remove sideband noise. The fi ltered signal is amplifi ed by
the 2nd IF AMP, and demodulated by the quadrature detector
with discriminator (X2).
The demodulated AF signal is applied to the RX AF circuits.
RX AF CIRCUITS (MAIN AND LOGIC UNITS)
• While operating in the DV mode
The demodulated AF signal is passed through the LPF (MAIN
UNIT: R118, R121, C122, C130, C135), and then applied to
the digital demodulation circuits on the LOGIC UNIT.
The AF signal from the MAIN UNIT is amplifi ed by the AF
AMP (LOGIC UNIT: IC13A, pins 1, 2) and passed through the
LPF (LOGIC UNIT: IC13B, pins 6, 7), and then applied to the
liner CODEC (LOGIC UNIT: IC15, pin 3) to be encoded in to
a digital audio signal.
The digital audio signal is demodulated by the DSP (LOGIC
UNIT: IC18), and then applied to the linear codec (LOGIC
UNIT: IC15) to be decoded into an analog audio signal.
The decoded AF signal is applied to the MAIN UNIT.
The AF signal is passed through the mode SW (MAIN UNIT:
IC8, pins 3, 4) and AF fi lters (MAIN UNIT: IC9B, pins 6, 7
and IC9C, pins 9, 10), and then applied to the D/A converter
(MAIN UNIT: IC11, pin 13) to be adjusted in level.
• While operating in the FM/FM-N mode
The demodulated AF signal is passed through the
LPF (R272,
C355), mode SW (MAIN UNIT: IC8, pins 1, 2) and AF fi lters
(MAIN UNIT: IC9B, pins 6, 7 and IC9C, pins 9, 10), and then
applied to the D/A converter (MAIN UNIT: IC11, pin 13) to be
adjusted in level.
The level-adjusted AF signal is amplifi ed by the AF power
AMP (MAIN UNIT: IC2, pin 1), and then output from the in-
ternal speaker (CHASSIS: SP1) or external speaker, through
the SP jack (MAIN UNIT: J4).
RF
LPF
LPF
BPF BPF
ANT
SW
D27,D29,D30
To the 1st IF circuits
From the TX AMP circuits
D32
D24,D25
D31,D33
IF
AMP
LPF
BPF
XTAL
46.35MHz
FI3D23D22
To the 2nd IF circuits
To the RF circuits
From the VCO
LIMIT
Q46
Q44
1st LO
LIMIT
BPF
CERAMIC
BPF
CERAMIC
BPF
Q38
X1
X2
From the 1st IF circuits
To the RX AF circuits
DISCRI
IC13
IF IC
FI2
15.3MHz
W/N
SW
FI1
Q36,D15
To the digital
demodulation circuits.
X3
REF
45.9MHz
FM
FM-N/DV
D16,D18,D19
LPF
LPF
DAFO
DDET
To the RX AF circuits
Q31
CODEC
LINEAR
DSP
IC15
IC13B
IC18
IC13A
RTONE
AMP
From the 2nd IF circuits
AF
AMP
J4
SP1
LPF
IC2
VO-
VO+
From the 2nd IF circuits
D/A
IC11
FILTER
SW
MODE
AF
IC9B,C
Q23
IC8
From the digital
demodulation circuits.
IC16
AFON
CHASSIS UNIT
[SP]
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