Icom IC-7100 Service Manual Addendum page 222

1ST RX IF CIRCUIT (MAIN UNIT)
The RX signal from the RF circuit is applied to the 1st IF
mixer (For the HF band: Q3231 and Q3232, For the VHF/
UHF band: D3252 and D3253), and mixed with the 1st LO
signal, resulting in the 124.487 MHz (WFM:134.732 MHz) 1st
RX IF signal.
The 1st RX IF signal is amplifi ed by the 1st RX IF AMP (Q4001),
and then passed through the 1st RX IF fi lter FI4101.
When the receiving mode is WFM, the 1st RX IF signal is
by-passed FI4101.
The fi ltered signal is further amplifi ed by another 1st IF AMP
(Q4201), and then applied to the 2nd RX IF circuit.
• 1ST RX IF CIRCUIT
FI4101
XTAL
BPF
Q4201
BW:15kHz
IF f0=124.487MHz
AMP
To the 2nd
RX IF circuit
BPF
BW:3MHz
f0=134.732MHz
• 2ND AND 3RD RX IF CIRCUITS
IC4505
To the digital
demodulation circuit
1st mixer
(V/UHF band TX/RX
and HF band TX)
1st IF: D3252,D3253
124.487MHz
134.732MHz(WFM)
From the RF circuit
(74.8MHz or above)
Q4001
1st LO
IF
1st mixer
AMP
(HF band RX)
Q3231,Q3232
From the RF circuit
(74.8MHz and below)
1st LO
IC4504
IC4601 FI4602
AF WFM
AM P DET
BW=280kHz
3IF 36kHz
IC4504
I C4501
I C4503
I C4502
IF
AM P
3LO
419kHz
2ND RX IF CIRCUIT (MAIN UNIT)
The 1st RX IF signal from the 1st RX IF circuit is applied
to the 2nd IF mixer (D4301 and D4302), and mixed with
the 124.032 MHz 2nd LO signal, resulting in the 455 kHz
(WFM:10.7 MHz) 2nd RX IF signal.
• The WFM mode
The 2nd RX IF signal is passed through the diplexer (L4304,
L4351, L4352, C4302, C4303, C4351) and 2nd RX IF fi lter
(FI4601), and then applied to the 2nd RX IF AMP (Q4601).
The amplifi ed signal is passed through another 2nd RX IF
fi lter (FI4602), and then applied to the IF IC (IC4601).
IC4601 contains an IF AMP and quadrature detector circuit,
and demodulates the WFM signal into the AF signal.
The demodulated AF signal is passed through the de-em-
phasis circuit (R4606, R4610, C4612, C4615 and C4616) to
obtain +6 dB of alteration of the amplitude-versus-frequency
characteristics, then amplifi ed by the AF AMP (IC4504), and
then applied to the digital demodulation circuit, through the
mode SW (IC4505).
• Other than WFM mode
The 2nd RX IF signal is passed through the diplexer (L4304,
L4351, L4352, C4302, C4303, C4351) and 2nd RX IF fi lter
(FI4351), and then applied to the 2nd RX IF AMP (Q4501),
through the TX/RX 2nd IF SW (IC4351). The amplifi ed signal
is applied to the 3rd IF mixer (IC4502), through another TX/
RX 2nd IF SW (IC4501), and mixed with the 419 kHz 3rd LO
signal, resulting in the 36 kHz 3rd RX IF signal.
The 3rd RX IF signal is applied to the 3rd RX IF AMP
(IC4504), through the TX/RX 3rd IF SW (IC4503). and then
applied to the digital demodulation circuit, through the mode
SW (IC4505).
FI 4601
Q4601
CERAMIC CERAMIC
IF
AM P
BPF BPF
BW=280kHz
Q4501
FI4351
I C4351
CERAMIC
IF
AM P
BW=20kHz
3-3
2IF
455kHz
10.7MHz(WFM)
D4301,D4302
DIPLEXER
From the 1st RX IF circuit
2LO
124.032MHz
BPF