Frequency Synthesizer Circuits - Icom IC-R9500 Service Manual Addendum

-VIDEO AM-DEMODULATION- (except for USA version)
The 2nd IF signal divide at the splitter is amplifi ed and fi ltered, then converted into the 3rd IF (video IF) signal at 3rd mixer (IC2201).
The converted video IF signal is amplifi ed, then passed through the video IF fi lters. The fi ltered video IF signal is applied to the
video demodulation IC and AM-demodulated.
The demodulated video signals are passed through Band Eliminate Filter (BEF; as the trap) to remove unwanted beat
components. The fi ltered signal is buffer-amplifi ed and output from the video jack on the CONNECT-B UNIT.
• VIDEO AM-DEMODULATION CIRCUIT
- 10dBm
Q2101
IF
2nd IF signal
ATT
AMP
from the RF-A UNIT
TR4_5M
Q2
Q1
IF
BUFF
AMP
TR5_5M
3-2 FREQUENCY SYNTHESIZER
OSC UNIT
The OSC UNIT supplies very high stability 10.000000 MHz
standard frequency signal generated by the OCXO (Oven
Controlled X'tal Oscillator). The oscillated reference
frequency signal is buffer-amplifi ed and amplifi ed and fi ltered
to remove harmonic components at the LPF. The filtered
reference frequency signal is applied to the PLL UNIT via
the buffer.
The reference frequency signal is also available from the
external reference frequency source (10.000000 MHz)
via [REF I/O] (CONNECT-B UNIT; J201). The reference
frequency signal from the CONNECT-B UNIT is passed
through the attenuators, BPF and switches, then buffer-
amplifi ed before being applied to the PLL UNIT.
• OSC CIRCUITS
From [REF I/O] (CONNECT-B; J201)
10MHz
Q61/Q62
BPF
AMP
EXT-REF IN
ATT
EXT-REF OUT
LPF
AMP
Q42
10MHz
• VCO-A, VCO-B, VCO-C LOOP
VCO1 BOARD
IC1001
VCO-C
LOOP
FIL
389.35~521.3MHz
VCO-B
514.35~639.35MHz
VCO-A
Ref 500kHz
DATA
IC1000
CK
PST1P
PLL
IC
10.5MHz
Q2181
IF
BPF ATT
AMP
48MHz
2nd LO signal
from the PLL UNIT
TR6_0M
BPF BPF
BPF BPF
TR6_5M
AGC
10.000.000 MHz
Standard signal
BUFF
Q70
LPF AMP
Q22
10MHz
2SC4081
Q21
X1
BUFF
(10.000000MHz OCXO)
317.8~391.3MHz
Q1102
Q1101
BUFF
Q1202
Q1201
BUFF
Q1302
Q1301
BUFF
LH1V
LH2V
LH3V
SPM5001
IC2201
ATT
TR4_5M
TRAP
TR5_5M
TRAP
TPSCC6.0MB
TR6_0M
IC101
TRAP
VIDEO FILTER
DETECT SW
TRAP
IC201/IC203
PLL UNIT
PLL UNIT supplies the LO (Local Oscillator) signals
(1st, 2nd, 3rd and 4th), still more the clock signals for
DSP circuits. To obtain physical strength for the VCO1,
VCO2, DOUBLER, FIL1 and FIL2 BOARDs, these circuits
are shielded and isolated perfectly, by being patterned
separately on different P.C. boards.
VCO1 BOARD
VCO1 BOARD has tree VCOs ;VCO-A, VCO-B and VCO-C.
VCO-A (Q1301), as an example, is a colpitts-typed oscillator
circuit, and its output signal is buffered by Q1302 and output
via diode switch. Q1303 controls the power supply for the
VCO, and the voltage of LH3V line adjusts the oscillation
level for suitable LO signal level.
The buffer-amplifi ed VCO output signals are divided by the
divider, and applied to the LO amplifier via attenuator (as
a pad). The amplified LO signals are applied to the RF-A
UNIT or FIL1 BOARD as the 1st LO signals, via fi lters and
amplifi ers.
The VCO-A is mounted on the nearest to VCO1 board to
reduce the signal loss. The resonators are employed strip
lines which had been used with SMD electric parts. The
oscillating frequency ranges are divide into three for wide
oscillation frequency coverage.
317.8~639.35MHz
IC1300
ATT
AMP
6dB
HYB
IC1351
ATT AMP
317.8~639.35MHz
3 - 3
TPSCC4.5MB
TPSCC5.5MB
Q301
FILTER
BUFF Composit video signal
SW
to the J601 (CONNECT-B UNIT)
IC202/IC204
TPSCC6.5MB
ATT
ATT
1st LO signals
to RF-A UNIT
To FIL1 BOARD