3Rd Tx If And 2Nd Tx If Circuits (Main Unit); Bpf Circuits; 1St Tx If Circuits (Rf-A Unit) - Icom IC-7410 Service Manual

3RD TX IF AND 2ND TX IF CIRCUITS (MAIN UNIT)

The 3rd TX IF signal from the modulation circuits is amplifi ed
by two AMPs (IC4661 and IC3601), and then applied to
the 3rd TX mixer (IC3621) to be mixed with the 3rd TX LO
signal from the PLL UNIT, resulting in the 455 kHz 2nd TX IF
signal.
The converted 2nd TX IF signal is amplifi ed by the IF AMP
(Q3631), and then passed though the 2nd TX fi lter (FI3641).
The fi ltered 2nd TX IF signal is amplifi ed by the 2nd TX IF
AMP (Q3651), and then applied to the 2nd TX mixer (D3671).
The 2nd TX IF signal is mixed with the 64 MHz 2nd TX LO
signal from the PLL UNIT, resulting in the 64.455 MHz 1st
TX IF signal.
The 1st TX IF signal is applied to the 1st TX IF circuits on
the RF-A UNIT.
• 3RD TX IF AND 2ND TX IF CIRCUITS
From the
I C4661 I C3601
Q3631
modulation
IC3621
circuits
IF
AMP
AMP
AMP
491 kHz
T3LO
From the PLL UNIT
64 MHz
T2LO
From the PLL UNIT

1ST TX IF CIRCUITS (RF-A UNIT)

The 1st TX IF signal from the 2nd TX IF circuits is passed
through the 1st TX IF filter (FI911) to remove unwanted
signals. The fi ltered signal is amplifi ed by the IF AMP (Q611),
and then applied to the 1st TX mixer (D651), through the
LPF.
The 1st TX IF signal is mixed with the 1st TX LO signal from
the PLL UNIT, resulting in the TX signal (TX frequency itself).
The converted TX signal is passed through the LPF, and
amplifi ed by the AMP (IC601), and then applied to the BPF
circuits.
• 1ST TX IF CIRCUITS
FI911
From the
64.455 MHz(BW=15 kHz)
2nd TX IF
Q611
circuits
XTAL IF
AMP
BPF
RF-A UNIT
To the
FI3641 64.455 MHz
Q3651
1st TX IF
D3671
circuits
CERAMIC
IF
BPF
BPF AMP
455kHz(BW=20k)
I C3675
LO
ATT ATT
AMP
To the
IC601
D651 BPF
circuits
IF
LPF LPF
AMP
64.485~
124.455 MHz
Q811
LO
LPF LPF
AMP
LPF

BPF CIRCUITS

The TX signal from the 1st TX IF circuits is passed through
an LPF or one of BPFs, depending on the transmitting
frequency, to remove unwanted signals contained in the TX
signal.
The fi ltered TX signal is amplifi ed by the YGR AMP (IC201),
and then applied to the PA-A UNIT, through the BPF.
• BPF CIRCUITS
From the
1st TX IF
circuits
1st TX LO
3 - 4
0.03-1.6 MHz
LPF
IC201
YGR
1.6-2.0 MHz
AMP
BPF HPF
2.0-4.0 MHz
BPF UNIT
BPF
4.0-8.0 MHz
BPF
8.0-11.0 MHz
BPF
11.0-15.0 MHz
BPF
15.0-22.0 MHz
BPF
22.0-30.0 MHz
BPF
50.0-54.0 MHz
BPF
30.0-50.0 MHz
54.0-60.0 MHz
BPF
To the
TX amplifier
circuits
BPF