![background image](http://html2.mh-extra.com/html/icom/ic-7100/ic-7100_service-manual-addendum_3610552223.webp)
3-4
AF
MUTE
From the 3rd RX IF circuit
Q251 Q252
IF
AM P
LPF
AF
AMP
A/D
SP1
J301
LPF
AF
AM P
D/A
Q401
OUTPUT
CTRL
LPF
LPF
LPF
LPF
Q403
AF
MUTE
Q404
DISPLAY UNIT
fc=3.5kHz
fc=89kHz
[PHONES/SP]
[EXT-SP]
fc=30.4kHz
fc=16kHz
Internal speaker
IC5213
IC5161
IC5071
IC5082
IC5082
IC5083A
IC5083B
IC5151
IC221
Q402
MAIN UNIT
DV-DSP
IF-DSP
IC5502
IC5001
From the TX AF circuit
IC5162
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
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).