Codan Radio Communications VT-3-150-SN User Manual
3-4
Audio Processor Board Instruction Manual
Voltage regulator U2A provides regulated +4.0V to all Op-amp stages. Optional potentiometer R14
can be installed (and JU15 removed) for special applications which need a voltage different than
+4.0V.
can be installed (and JU15 removed) for special applications which need a voltage different than
+4.0V.
Data normally enters at P4-3, the Direct Modulation Input. From there, it has many routes that it
can go. JU43 allows direct or on-board capacitive coupling. Op-amp U2B can be configured as a
buffer with a DC offset to handle input data that has a positive DC voltage offset. The data signals
can be sent to gain buffers U2C and U2D through potentiometer R48. Jumper JU14 is normally
installed so that the output from U2D provides the correct data polarity when using two port
modulation.
can go. JU43 allows direct or on-board capacitive coupling. Op-amp U2B can be configured as a
buffer with a DC offset to handle input data that has a positive DC voltage offset. The data signals
can be sent to gain buffers U2C and U2D through potentiometer R48. Jumper JU14 is normally
installed so that the output from U2D provides the correct data polarity when using two port
modulation.
X
Y
DEV IATIO N
CONT R O L
CONT R O L
LOW FREQUENCY / DIRECT
MODULATION OUTPUT
MODULATION OUTPUT
X
Y
X
Y
X
Y
X
Y
VOICE + SUBAUDIBLE
DCS, LTR
X
Y
TCXO DC
LEVE L
LEVE L
A D J U ST
T CXO MO D ULATIO N
L EVEL A DJ UST
1
P3
2
P4
JU37
2
1
3
JU22
+9.5V CONTINUOUS
4.7uF
C45
4.7uF
C28
1
2
3
R29
50K0
50K0
R55
49K9
49K9
R75
10K0
10K0
E
B
C
Q1
BC817-25
BC817-25
+8.0V SWD
JU6
JU31
R44
0R0
0R0
R45
N/I
N/I
C12
1.0nF
1.0nF
R54
SEL
SEL
1
2
3
R36
50K0
50K0
JU32
SEL
R32
JU29
47uF
C34
R12
N/I
N/I
R79
49K9
49K9
JU7
In+
In-
Gnd
V-
Vout
V+
Rx
Div/Clk
1
2
3
4
8
7
6
5
U4
LTC1569-6
LTC1569-6
R66
22K1
22K1
R67
30K9
30K9
R68
3K48
3K48
R69
2K00
2K00
+8.0V SWD
P11
P12
P9
P10
9
10
8
U3
MC33174
c
0R0
R72
0R0
R58
1
2
C21
1.0uF
1.0uF
1
2
C6
1.0uF
1.0uF
R37
49K9
49K9
R34
49K9
49K9
4.0V
C24
10nF
10nF
+8.0V SWD
4.0V
JU23
TP7
TP8
TP9
SEL
R81
JU41
10nF
C41
R86
10K0
10K0
3
2
1
R83
50K0
50K0
R53
N/I
N/I
R80
27K4
27K4
+8.0V SWD
1
2
3
JU35
R78
10K0
10K0
2
3
1
JU39
1
2
3
JU34
JU38
C23
330pF
330pF
C44
330pF
330pF
13
12
14
U3
MC33174
MC33174
d
R35
SEL
SEL
JU8
100nF
C27
1.0uF
C33
1.0uF
C40
1.0uF
C47
1.0uF
C46
1
2
3
JU25
R22
49K9
49K9
R21
49K9
49K9
1
2
3
4
5
U5
TC4S66F
1
2
3
4
5
U6
TC4S66F
TC4S66F
4.0V
R50
49K9
49K9
R88
49K9
49K9
JU26
4.0V
C55
100nF
100nF
JU44
33nF
C56
+9.5V CONTINUOUS
R77
20K0
20K0
JU18
2
1
3
JU19
2
3
1
JU21
1
2
JU45
R89
100R
100R
Tx Audio Control
Figure 6
TX Audio Control Circuitry
A single TX Audio control line P4-4 has 2 functions. It can be configured to switch U3D inputs
between data and voice. Alternately, it can be configured to remotely switch between wideband and
narrowband applications by switching between the regular audio path and one carrying half the
audio level as determined by resistive divider comprised of R22 and R21.
between data and voice. Alternately, it can be configured to remotely switch between wideband and
narrowband applications by switching between the regular audio path and one carrying half the
audio level as determined by resistive divider comprised of R22 and R21.
Due to the complex nature of data modulation methods, the actual configurations and values of
SELected components for LTR, DCS, Paging are contained in a separate applications manual
“AM20-DMS”.
SELected components for LTR, DCS, Paging are contained in a separate applications manual
“AM20-DMS”.