Transmitter Circuits - Icom IC-7100 Service Manual Addendum

3-2 TRANSMITTER CIRCUITS

TX AF CIRCUIT (MAIN UNIT)
The audio signal from the microphone (MIC signal) is applied
to the MAIN UNIT, through the MICROPHONE CONNECTOR
(MIC UNIT: J1), and then amplifi ed by the MIC AMP (IC141).
The amplifi ed signal is applied to the AF AMP (IC5163),
through the LPF (IC5161).
The audio signal from the accessory socket [ACC] on the
rear panel, is passed through the MIC line SWs (IC5211 and
IC5212), TX/RX AF SW (IC5213) and LPF (IC5161), and
then applied to the AF AMP (IC5162).
The amplifi ed signal is applied to the A/D converter (IC5071)
and converted into a digital audio signal.
The converted digital audio signal is applied to the DSP (Ana-
log mode: IC5001 or DV mode: IC5502), and demodulated
and processed. The demodulated signal is applied to the D/A
converter (IC5071), converted into the 36 kHz 3rd TX IF sig-
nal, and then amplifi ed by the active LPF (IC5081).
The amplifi ed 3rd TX IF signal is applied to the 3rd TX IF cir-
cuit, through the 3rd TX IF SW (IC5111).
• TX AF CIRCUIT
IC5081 IC5081
TX IF IC5111
36kHz
IF
LPF
AM P
IC141 IC5163
IC5161
MIC AF
LPF
AMP
AM P
MAIN UNIT
I C5001
IC5071
IF-DSP
D/A
I C5502
A/D
DV-DSP
1
2
3
4
5
MIC
6
7
8
J1304
1
2
3
MIC
4
5
6
7
8
DISPLAY UNIT
3RD TX IF CIRCUIT (MAIN UNIT)
The 3rd TX IF signal from the modulation circuit is applied
to the 3rd TX mixer (IC4502), through the TX/RX 2nd IF SW
(IC4501), mixed with the 419 kHz 3rd TX LO signal, resulting
in the 455 kHz 2nd TX IF signal.
The converted 2nd TX IF signal is applied to the 2nd TX IF
AMP (Q4401) through another 2nd IF SW (IC4503). The am-
plifi ed signal is applied to the 2nd IF fi lter (FI4351), through
the 2nd IF SW (IC4351), to remove unwanted signals.
The fi ltered 2nd TX IF signal is applied to the 2nd TX IF
circuit, through the diplexer (L4304, L4351, L4352, C4302,
C4303, C4351).
• 3rd TX IF CIRCUIT
From the 3rd TX IF circuit
Q4251
D4301,D4302
IF
AMP
TX IF
124.487 MHz
2LO
124.032MHz
2ND TX IF CIRCUIT (MAIN UNIT)
The 2nd , from the 3rd TX IF circuit is applied to the 2nd IF
mixer (D4301 and D4302), then mixed with the 124.032 MHz
2nd TX LO signal, resulting in the 124.487 MHz 1st TX IF
signal.
The converted 2nd TX IF signal is amplifi ed by the 1st TX IF
AMP (Q4251), passed through the 1st IF fi lter (FI4101) to
remove unwanted signals, and then to the variable attenuator
(D4053 and D4054) to adjust the signal level.
The level-adjusted 1st TX IF signal is applied to the 1st TX
IF circuit.
• 2nd TX IF CIRCUIT
I C4351
Q4401
IF
AM P
I C4503
From the TX AF circuit
3-5
To the 1st TX IF circuit
FI4101
D4053,D4054
PIN
XTAL
BPF ATT
BW:15kHz
f0=124.487MHz
To the 2nd TX IF circuit
2nd RX IF circuit
FI4351
DIPLEXER
CERAMIC
BPF
BW=20kHz
MAIN UNIT
I C4501
I C4502
3LO
419kHz
TX IF
455 kHz