Mlo1/Mlo2; Reference Signal Generator Of The Main Receiver Block, Mlo1/Mlo2 - Kenwood TS-990S Service Manual

1-3. MLO1/MLO2

■ MLO1 (1st Local Oscillator for Main Receiver)
The VCO (Q4) oscillates at 393.6MHz. It is applied to pin
5 of the PLL (IC2) via the BPF. The 40MHz reference signal
is applied to pin 8. The signal which is applied to pin 5 of the
PLL (IC2) is frequency-divided by N and the reference signal
which is applied to pin 8 is frequency-divided by R. They are
phase-compared to lock the phase, and the phase-locked
393.6MHz signal is used as the reference of the DDS (IC3).
The output signal from the DDS (IC3) is amplifi ed by the
wide-band amplifi er (IC9). When using the DDS (IC3) output
directly as the MLO1, it is sent via the BPF, buffer (IC23),
amplifi er (Q99) and BPF. When using the VCO as the MLO1,
a signal which is amplifi ed by the wide-band amplifi er (IC9)
is applied to pin 8 of the PLL (IC17) via the BPF.
There are four VCOs (Q25, Q26, Q38 and Q39) for the
Q3 IC2 Q4
PLL
393.6M
AMP
Q8
AMP
X1 Q10 IC13 Q27
DDS
19.2M AMP Buffer
Q5 Q11
CN33 D7
R10M
10M
AMP
Buffer
Q9
AMP
D28
Fig. 2 Reference signal generator of the main receiver block, MLO1/MLO2
CIRCUIT DESCRIPTION
Q25, Q26, Q38, Q39
IC17
Q44
82.78~ 115.48~
92.48MHz 128.992MHz
PLL
AMP
96.48~ 127.48~
107.48MHz 138.992MHz
Q35
AMP
D12
Q1 IC3 IC9
DDS AMP
AMP
CF1 Q34 D23,25 Q46 IC18
PLL
AMP
AMP
D19,20
D13 IC14
ERDET
AMP
MLO1. They oscillate at 82.78 to 138.992MHz. These oscil-
lation outputs from the VCOs is applied to pin 5 of the PLL
(IC17). The signal which is applied to pin 5 is frequency-
divided by N and the signal which is applied to pin 8 is
frequency-divided by R. They are phase-compared to lock
the oscillating frequency, and used as a VCO output. The
oscillation output from the VCO is applied to the frequency
dividers (IC19, IC20, IC21 and IC22) via the amplifi er (Q45)
where the frequency is divided by 4, 8, or 10. The frequency
divided signal is passed through the amplifier (Q99) and
BPF, and is sent as the MLO1.
■ MLO2 (2nd Local Oscillator for Main Receiver)
The DDS (IC26) generates the MLO2 which is used
for the detector. The DDS (IC26) output signal is sent from
CN21 as the MLO2.
IC19 IC20
Q45
1/2 1/5
AMP
IC21
1/2
IC22
1/2
IC23
D29 D33 D37
Buffer
D49
X2 Q78
Q79
VCXO
Buffer AMP
20M
Doubler
Q82
AMP
IC24 IC25
Q51 Q81
1/2 1/2
AMP AMP
TS-990S
D42 D50
D39
D43 D51
Q99
D44 D52
D40
AMP
D45 D53
D38
D46 D54
D41
D47 D55
D48 D56
Q84 Q80 IC26
DDS
AMP
AMP
Q85
AMP
Q86
AMP
CN22
MLO1
CN21
MLO2
CN19
R40M
CN20
SCREF
5