4-1
SECTION
4
.
CIRCUIT
DESCRIPTION
• RF CIRCUIT
• 1ST RX IF CIRCUIT
• 2ND RX IF CIRCUIT
• 3RD IF CIRCUIT
ATT
ATT
LPF
LPF
BPF
BPF
BPF
BPF
BPF
BPF
LPF
HPF
SWR
DET
RF
AMP
BPF
PA-A UNIT
MAIN-A UNIT
0.03-1.59 MHz
1.60-2.49 MHz
2.50-3.99 MHz
4.00-5.99 MHz
6.00-8.99 MHz
9.00-12.99 MHz
13.00-19.99 MHz
20.00-29.99 MHz
RX
TX
TX circuits
20 dB
TX
RX
fc=32 MHz
fc=30 MHz
Q1116,Q1117
D1406
To the 1st RX IF circuits
D1131
D1129
2
1
1
1
D
0
2
1
1
D
D1121
D1122
D1123
D1124
D1125
D1126
D1127
D1108
D5086,D5087
D5088,D5089
D5084,D5085
D5090,D5091
RX MUTE
D1107
Q1101
RL5001
D5001
D5002
D1113
D1106
D1114
D1115
D1116
D1117
D1118
D1119
D1133
D1142
IF
AMP
BPF
XTAL
IF
AMP
BW=15 kHz
FI1401
Q1414
Q1404-Q1407
From the
RF circuits
To the 2nd RX
IF circuits
D1403
1st RX LO signal
D1405
D1408
D1411
64.455 MHz 1st RX IF
Q1810
BUFF
IF
AMP
IF
AMP
BPF
CERAMIC
L1446
Filter
D1813
FI1402
Q1411
Q1415
From the 1st
RX IF circuits
To the 3rd RX
IF circuits
2nd RX LO signal
D1416
D1418
D1420
Q1413
Q1412
D1812
LPF
IC1403
3rd TX IF
IC1402
To the demodulator
circuits
From the 2nd RX
IF circuits
3rd RX LO signal
D1412
36 kHz 3rd IF
3rd IF SW
4-1 RECEIVER CIRCUITS
RF CIRCUIT (PA-A AND MAIN-A UNITS)
The RX signal from the antenna is passed through the SWR
detect circuit (PA-A UNIT; D5001, D5002), TX/RX line SW
(PA-A UNIT; RL5001) and LPF (PA-A UNIT; L5001, L5002,
C5101–C5105), and then applied to the MAIN-A UNIT.
The RX signal from the PA-A UNIT is passed through or
bypassed the attenuator circuit (MAIN-A UNIT; R1103,
R1106, R1108), RX mute SW (MAIN-A UNIT; Q1101,
D1107), TX/RX line SW (MAIN-A UNIT; D1108), and then
applied to the filter circuits.
The RX signal is passed through an LPF or one of BPFs,
depending on the operating frequency, to remove unwanted
out-of-band signals. The filtered RX signal is applied to or
bypassed the preamplifier circuit.
The RX signal from the filter circuits is applied to or
bypassed the preamplifier.
When the Preamplifier function is activated, the RX signal
is amplified by the preamplifier (MAIN-A UNIT; Q1116,
Q1117).
The amplified or bypassed RX signal is applied to the 1st
RX IF circuits.
1ST RX IF CIRCUIT (MAIN-A UNIT)
The RX signal from the preamplifier circuit is applied to the
1st RX IF mixer (Q1404–Q1407) to be mixed with the 1st
RX LO signal, resulting in the 64.455 MHz 1st RX IF signal.
The 1st RX IF signal is amplified by the 1st RX IF AMP
(Q1810) and passed through the 1st RX IF filter (FI1401).
The filtered 1st RX IF signal is amplified by another 1st RX
IF AMP (Q1414), and then applied to the 2nd RX IF circuits.
2ND RX IF CIRCUIT (MAIN-A UNIT)
The 1st RX IF signal from the 1st RX IF circuits is applied
to the 2nd RX IF mixer (D1812, D1813) to be mixed with
the 2nd RX LO signal, resulting in the 455 kHz 2nd RX IF
signal. The 2nd RX IF signal is passed through the trans-
former-coupled filter (L1446) and 2nd RX IF filter (FI1402),
and amplified by the 2nd RX IF AMPs (Q1415, Q1412 and
Q1413), and then applied to the 3rd RX IF circuits, through
the buffer (Q1411).
3RD RX IF CIRCUIT (MAIN-A UNIT)
The 2nd RX IF signal from the 2nd RX IF circuits is applied
to the 3rd RX IF mixer (IC1402) to be mixed with the 3rd RX
LO signal, resulting in the 36 kHz 3rd RX IF signal.
The 3rd RX IF signal is passed through the 3rd IF SW
(IC1403) and LPF (L1454. C1550, C1553), and then applied
to the demodulator circuits on the DSP1-A UNIT.
