Frequency Synthesizer Circuits; Voltage Block Diagram - Icom IC-F3001 Service Manual Addendum

TX AMPLIFIERS
The buffer amplified signal from the LO SW (D5) is
amplified by the pre-drive AMP, drive AMP, and power AMP
in sequence, to obtain TX power. The amplified TX signal
is passed through the antenna SW and the LPF, which
eliminates harmonics, and then fed to the antenna.
APC CIRCUITS
D1 and D2 rectify a portion of the TX signal to direct current,
and the APC AMP compares the voltage and the TX power
control reference voltage, "T1." The resulting voltage controls
the gain of the power and drive AMPs to keep the TX power
constant.
• TX AMPLIFIERS AND APC CIRCUIT
Q3 Q2
From the
TX VCO
PRE
PWR
DRIVE
DRIVE
AM P
AM P
To the RX circuits
All manuals and user guides at all-guides.com
ANT
D1,D22
Q1
ANT
LPF
SW
IC1
APC PWR
D1,D2
AMP
T1 DET
Q6
TMUT
MUTE
SW

4-3 FREQUENCY SYNTHESIZER CIRCUITS

The RX VCO is composed of Q13, D11 and D12. The VCO
output signal is buffer-amplified by two buffers and applied
to the 1st IF mixer, via the LO SW (D6) and the attenuator.
The TX VCO is composed of Q14 and D14–D16. The VCO
output signal is buffer-amplified by two buffers and applied
to the 1st IF mixer, via the LO SW (D6) and the LPF.
A portion of oscillated signal from each VCO is fed back to
the PLL IC via the buffer and the LPF.
The applied VCO output signal is divided and phase-
compared with a 15.3 MHz reference frequency signal from
the TCXO, which is also divided. The resulting signal is
output from the PLL IC, and DC-converted by the loop filter,
and then applied to the VCO as the lock voltage.
When the oscillation frequency drifts, its phase changes
from that of the reference frequency, causing a lock voltage
change to compensate for the drift in the VCO oscillating
frequency.
• FREQUENCY SYNTHESIZER CIRCUITS
D11
LV
ADJ
LOOP
X2
FILTER
IC60
BAL
15.3MHz
BUFF
TCXO
REF
D14
LVA
LV
ADJ
Q26
IC2
PLL
X3
IC
LPF
SO,SCL,PLST
45.9MHz
IF IC
BPF
IC3

4-4 VOLTAGE BLOCK DIAGRAM

Q74-76
PWON
+5V
VCC REG
S5
F51
4 - 3
RX VCO
Q13,D12
LV
D5,D6
Q10
Q8
LO
BUFF BUFF To the TX AMPs
SW
TX VCO
Q14,D16
ATT
Q9
BUFF
Q23
1st IF mixer
Q73
T5C
T5 T5V
To the TX circuits
REG
Q72
R5C
R5 R5V
To the RX circuits
REG
Q71
S5 S5V
To both RX and TX circuits
S5C REG
+5V
To both RX and TX circuits
IC54
CPU5 CPU5
To the logical circuits
REG