Icom IC-9100 Service Manual page 17

VHF RF CIRCUITS (RF-B UNIT)
VHF band RX signal from the antenna connector [144MHz
ANT] (CHASSIS; J1) is passed through the SWR detecter
(PA-B; D801, D811), LPF (PA-B; L771–L773, C771–C777),
TX/RX SW (PA-B; RL751) and LPF (PA-B; L763, C770), and
then applied to the RF-B UNIT.
The RX signal from the PA-B UNIT is passed through the
HPF (L1353, L1354, C1355–C1357), and then passed
through or bypassed the attenuator circuit (D1351–D1354,
R1352–R1354), depending on the setting.
The RX signal, which is passed though or bypassed the
attenuator circuit (D1351–D1354, R1352–R1354), is passed
through the BPF (D1301, D1302, L1301, L1302, C1301,
C1302), and then applied to the RF AMP (Q1251).
The amplified RX signal is passed through the two-
staged BPF (D1209–D1211, L1202, C1203, C1206,
and D1202–D1204, L1201, C1201, C1205) and HPF
(L1111–L1114, C1111–C1114, C1116–C1117, C1119), and
then applied to the 1st RX IF circuits.
• VHF/UHF RF CIRCUITS
To the VHF 1st RX IF circuits
To the UHF 1st RX IF circuits
HF 1ST RX IF CIRCUITS (RF-A UNIT)
The RX signal from the BPF UNIT is passed through the
LPF, which removes unwanted signals (60 MHz and higher),
and then applied to the 1st RX IF mixer (Q721–Q724) to be
mixed with the 1st RX LO signal (64.485–124.455 MHz) from
the PLL UNIT, resulting in the 64.455 MHz 1st RX IF signal.
The 1st RX IF signal is amplified by the 1st RX IF AMP
(Q741) and passed through one of the 1st IF fi lters (FI911;
FL-434, or optional FL-430 or FL-431), which has different
passband widths, according to the IF fi lter setting.
The fi ltered 1st RX IF signal is amplifi ed by the RX IF AMPs
(Q1051 and Q1071, Q1072), and then applied to the 2nd RX
IF circuits.
• HF 1ST RX IF AND 2ND RX IF CIRCUITS
I C1222 I C1222
To the demodulator circuits
90deg
Σ
Q1141 I C1121
LO
ATT
2nd RX LO BUFF
AMP
from PLL UNIT
Q1251
VRX
PRE
HPF BPF BPF
AMP
RF-B UNIT
I C2251
URX
RF
BPF BPF
AMP
Q1071/Q1072
I C1221 Q1201
D1102
IF IF
BUFF
AMP AMP
Q1251
I C1221
D1101
IF
BUFF
AMP
I C1121
BUFF
IC1121
BUFF
90deg
UHF RF CIRCUITS (RF-B UNIT)
UHF band RX signal from the antenna connector [430MHz
ANT] (CHASSIS; J2) is passed through the SWR detecter
(PA-B; D501, D511), LPF (L451, L452, C451–C455), TX/
RX SW (PA-B; D471–D473) and LPF (L471, C471, C472,
C475), and then applied to the RF-B UNIT.
The RX signal from the PA-B UNIT is passed through the HPF
(L2361, L2362, C2361–C2363, C2359), and then passed
through or bypassed the attenuator circuit (D2351–D2354,
R2352, R2354, R2355), depending on the setting.
The RX signal, which is passed though or bypassed the
attenuator circuit (D2351–D2354, R2352, R2354, R2355),
is passed through the BPF (D2301, D2302, L2301, C2301,
C2302), and then applied to the RF AMP (Q2251).
The amplified RX signal is passed through the two-
staged BPF (D2201–D2203, L2204, C2202, C2204, and
D2204–D2206, L2205, C2205, C2206) and HPF (L2210,
C2210), and then applied to the 1st RX IF circuits.
D1352-D1354,
D1351
ATT HPF
D2351-D2354
ATT HPF
UHF TX Circuits
HF 2ND RX IF CIRCUITS (RF-A UNIT)
The 1st RX IF signal from the 1st RX IF circuits is divided
into two paths, and then each signal is applied to the 2nd RX
IF mixers (the image reduction mixers; D1102/D1101) to be
mixed with the 2nd RX LO signal (64.491 MHz) from the PLL
UNIT, resulting in the 36 kHz 2nd RX IF signal.
The image reduction mixer removes image frequency
components by using two LO signals which are 90 degrees
phase-shifted from each other.
The 2nd RX IF signals are independently amplified by the
buffers (Q1201/Q1251) and IF AMPs (IC1221).
These amplifi ed 2nd RX IF signals are 90 degrees phase-
shifted and combined by the combiner (IC1222), and then
applied to the MAIN UNIT.
FI911
64.455MHz(BW=15kHz)
Q1051
IF XTAL
AMP BPF
FL-430(Optional)
64.455MHz(BW=6kHz)
XTAL
BPF
FL-431(Optional)
64.455MHz(BW=3kHz)
XTAL
BPF
3 - 2
RL751
D801/D811
TX/RX SWR
LPF
LPF
SW DET
To the VHF TX Circuits
PA-B UNIT
UHF ANT
D501/D511
L407CD
TX/RX SWR
LPF
SW DET
Q721/Q722/
fc=60MHz
Q741
Q723/Q724
From the preamplifier circuits
IF
ATT LPF
AMP
Q811
64.485~
LO
124.455 MHz
LPF
AMP
RF-A UNIT
VHF ANT
1st RX/TX LO
LPF
from PLL UNIT
LPF