Pa Unit; Filter Unit; Usb Controller; Tx Amplifiers And Lpfs - Icom IC-7200 Service Manual

• 1st LO GENERATOR CIRCUIT
DDS circuit is employed for LO signal generation; no
PLL circuit is used with the IC-7200. This provides
extremely high frequency stability against temperature
and vibration.
The 32 MHz reference frequency signal from the TCXO
(X2011) is buffer-amplified by Q2011 and amplified by
IC2011. The 8th harmonic component (256 MHz) in the 32
MHz reference frequency signal is extracted and amplified
by IC2151 to the level needed for the DDS. The amplified
256 MHz reference signal is applied to the DDS (IC2541)
as the master clock signal.
The 32.2425–64.2275 MHz signals are output from the
DDS, and doubled by D2572. The doubled signals are
used as the 1st LO frequencies. The 1st LO signals are
amplified by IC2601, filtered by the appropriate BPF to
remove unwanted frequency components, then applied
to the 1st LO AMP.
• OTHER LO GENERATOR CIRCUIT
The 32 MHz reference signal is also used for the another
DDSs of 2nd and 3rd LO signal generation, as well as the
DSP.
The 32 MHz reference signal from IC2011 is adjusted
its wave form, and divided by two by IC2042, then the
divided reference signal (16 MHz) is applied to the DDS
(IC2043) as the master clock signal. The DDS outputs
439.375 kHz signal as the 3rd LO.
The doubled reference signal (64 MHz) signal is
amplified by IC2091, and used as the 2nd LO.
• FREQUENCY CONFIGURATION
IF Signal Frequency
1st RX IF 64.455 MHz
2nd RX IF 455 kHz
3rd RX IF 15.625 kHz
3rd TX IF 15.625 kHz
2nd TX IF 455 kHz
1st TX IF 64.455 MHz
TX signal (*)
*; Refer to "SPECIFICATIONS."

• USB CONTROLLER

By connecting the PC through the USB connector
(J3202; type B), IC-7200 can be controlled by a PC.
The communication with the PC is accomplished by
connecting to the USB audio IC (IC3202) and UART
bridge (IC3203) through the USB hub (IC3201).
IC3202 converts the analog AF signals into the digital
audio signals (A/D conversion), and converts the digital
audio signals from the PC into the analog AF signals
(D/A conversion). IC3203 controls the transceiver from
connected PC using CI-V commands.
LO Signal Frequency
1st RX LO 64.485–124.455 MHz
2nd RX LO 64.000 MHz
3rd RX LO 439.375 kHz
3rd TX LO 439.375 kHz
2nd TX LO 64.000 MHz
1st TX LO 64.485–124.455 MHz
– –

3-3 PA UNIT

The PA UNIT is composed by power AMP which
amplifies the YGR output signal from the RF UNIT to the
TX output power, power supply line control circuits and
cooling fan control circuit.
• POWER AMP
The TX signal from the RF UNIT is amplified by the pre-
drive AMP (Q1) on the entire band (HF to 50MHz band).
The amplified TX signal is passed through L1, and
amplified by the push-pulled drive AMP (Q2, Q3). These
AMPs (Q1 to Q3) are individually gain-adjusted so that
the frequency characteristic of TX signal is flat one by
feeding back the 180-degree phase-shifted signal.
The amplified TX signal from the drive AMP (Q2, Q3)
is passed through L2 and applied to the power AMP
(Q4, Q5). The TX signal is power-amplified to the 100 W
(max.) of output power. The power-amplified TX signal is
entered to the FILTER UNIT via J9, and passed through
a BPF corresponds to the TX frequency.
• POWER SUPPLY LINE
When the power SW on the FRONT panel is pushed,
Q7 turns RL1 ON and the 13.8 V DC is supplied to the
"P14V" line.
• COOLING FAN CONTROL CIRCUIT
The cooling fan control circuit is also equipped on the
PA UNIT. The cooling fan control voltage "FANV" is
applied to the base terminal of Q131, and the change of
the volatage causes the rotation speed of cooling fan.

3-4 FILTER UNIT

The FILTER UNIT is composed by LPFs which reduces
the harmonic components in the TX signal to be less than
–50 dB.
• LPF
The LPF stage is composed by seven Chebyshev-typed
LPFs which have different cut-off frequencies. The TX
signal passes through the one of 7 LPF according to the
TX frequency. A switching relay is used for LPF selection
on both input and output terminals for each LPF.

- TX AMPLIFIERS AND LPFs -

RF UNIT
IC181
YGR
ATT
AM P
Q1 Q2,Q3
PRE
DRIVE
DRIVE
AMP
PA UNIT
3 - 3
From BPFs
<2.0MHz
S8 S2
LPF
SW12 SW12
2.0-5.0 MHz
S9 S3
LPF
SW12 SW12
5.0-8.0 MHz
S10 S4
LPF
SW12 SW12
8.0-15.0 MHz
S11 S5
LPF
Q4,Q5
SW12 SW12
PWR
AM P
15.0-22.0 MHz
S12 S6
LPF
SW12 SW12
22.0-30.0 MHz
S13 S7
LPF
SW12 SW12
30.0-54.0 MHz
S13 S7
LPF
SW12 SW12
FILTER UNIT
To antenna