Icom IC-7100 Service Manual Addendum page 223

DIGITAL DEMODULATION CIRCUIT (MAIN UNIT)
The 3rd RX IF signal (and frequency-demodulated signal in
the WFM mode) is passed through the TX/RX IF SW (IC5213)
and LPF (IC5161), and then applied to the IF AMP (IC5162).
The amplifi ed signal is applied to the CODEC (IC5071).
IC5071 is a 24-Bit 192 kHz Stereo Audio CODEC and con-
tains D/A and A/D converters inside.
The applied signal is converted into a digital audio signal by
the A/D converter inside, and then applied to the DSP (Ana-
log mode: IC5001 or DV mode: IC5502).
The digital audio signal is demodulated and processed by the
DSP, and then applied to the D/A converter in the CODEC
(IC5071), to be converted into an analog audio signal.
The analog AF signal is amplifi ed by the active LPF (IC5082),
and passed through two LPFs (IC5083A and IC5083B),
whose cut-off frequencies are 16 kHz and 3.5 kHz.
In the WFM mode, the AF signal is passed through only the
16 kHz LPF (IC5083A).
The fi ltered signal is applied to the AF output circuit, through
the mode SW (IC5151).
• DIGITAL DEMODULATION AND AF OUTPUT CIRCUITS
From the 3rd RX IF circuit
fc=30.4kHz fc=89kHz
LPF LPF
Q251 Q252
DISPLAY UNIT
Q401
OUTPUT
Q403
IC5213
From the TX AF circuit
IC5083B IC5083A
IC221 IC5151
LPF
AF
AMP
fc=3.5kHz fc=16kHz
AF
[EXT-SP]
MUTE
Q402
[PHONES/SP]
CTRL
J301
Q404
SP1
Internal speaker
AF
MUTE
AF OUTPUT CIRCUIT (MAIN UNIT)
The RX AF signal from the digital demodulation circuit is am-
plifi ed by the AF AMP (IC221), and passed through two LPFs
(L231, R231, C231, C232 and L232, R233, R234, C233 to
C235).
The RX AF signal is output to the internal speaker, through
the AF mute SW (Q403 and Q404).
The AF signal is output to external speaker or headphones,
through the AF output controller (Q401 and Q402), when it is
connected to the [PHONES/SP] jack (DISPLAY UNIT: J402),
The AF signal is also output to the external speaker, through
the AF mute SW (Q251 and Q252), when it is connected to
the [EXT-SP] jack (MAIN UNIT: J191).
IC5071
IC5162
IC5161
IF
LPF
AM P
I C5082 I C5082
AF
LPF LPF
AM P
3-4
I C5001
IF-DSP
A/D
I C5502
D/A
DV-DSP
MAIN UNIT