UBZ-LJ8
2
Frequency Configuration
CIRCUIT DESCRIPTION
Receiver System
■
Front End
The high-frequency signal received from antenna passes
through a LPF (Low pass filter : components between ANT
and C73) to filter out unwanted high frequency signal. A
switch diode system (D8, L32 and D10) allows this signal to
pass through and enters the BPF (Band pass filter : L31) to
eliminate unwanted signal when receiving.
The resulting signal is amplified by high-frequency ampli-
fier (Q9) and goes to the first mixer (Q10).
■
First Mixer
The amplified signal that reaches Q10 is mixed with the
first local signal from a VCO to produce a first IF signal
(21.7MHz).
(Receive frequency – First local frequency
= First IF frequency = 21.7MHz)
The first IF signal passes through MCF (Monolithic crystal
filter) XF1 to eliminate unwanted components.
The first IF signal is amplified by IF amplifier (Q11) before
going into FM IC (IC2).
BPF
446MHz
MIX, IF
DET
AF
AMP
MIC
AMP
RF
AMP
RF
AMP
RF
AMP
PLL
VCO
1st MIX
21.7MHz
MCF
21.25MHz
21.25MHz
SP
MIC
TCXO
Simplex
446.00625~
446.09375MHz
Simplex
424.30625~
424.39375MHz
LPF
RF
AMP
ANT
Simplex
446.00625~446.09375MHz
ANT
SW
Fig. 1
Frequency configuration
Reception method
Double super heterodyne
1st IF frequency
21.7MHz (Lower)
2nd IF frequency
450kHz (Lower)
Transmission method
VCO direct amplification
Modulation
Variable reactance phase modulation
Table 1
MIX,
DET
SP
ANT
ANT
SW
D8,D10
L32
RF AMP
Q9
IF AMP
Q11
AF AMP
IC203
1st MIX
Q10
LPF
MCF
XF1
21.7MHz
FM IC
IC2
BPF
L31
446MHz
1st local OSC (PLL)
2nd local OSC
Fig. 3
Receiver front end and Mixer circuit
Fig. 2
Receiver section configuration
VCO
1st local
OSC
Q10
XF1
Q11
3R
3R
FM IC
L32
LPF
D8
3T
ANT
D10
Q9
3R
L31
Item
Rating
Nominal center frequency (fo)
21.7MHz
Pass bandwidth
±
3.75kHz or more at 3dB
Attenuation bandwidth
±
14kHz or less at 40dB
Ripple
1dB or less
Insertion loss
3.5dB or less
Ultimate attenuation
80dB or more (fo
±
910kHz)
Spurious responses
40dB or more (fo
±
1MHz)
Terminating impedance
850
Ω±
5% // 5pF
±
0.5pF
Table 2
MCF (L71-0616-05) : TX-RX Unit XF1
Item
Rating
Nominal center frequency (fo)
450kHz
6dB bandwidth
±
4.5kHz or more
50dB bandwidth
±
10kHz or less
Ripple (450kHz
±
3kHz)
3dB or less
Guaranteed attenuation (
±
100kHz)
40dB or more
Insertion loss
4dB or less
I/O matching impedance
2.0k
Ω±
10%
Table 3
Ceramic filter (L72-0974-05) : TX-RX Unit CF1