Furuno FAR-2107 Series Service Manual page 419

J821
1.SDATA
2. CLK
3. DATEN
4, 7, 11. GND
5. VBW B
6. VBW A
8. STC DETECT
9. TUNE GAIN
10. TUNE IND
12. MSB ENABLE
13. TUNE GATE N
14. SAMPLE HOLD
J822
1. D MONO OUT
2. PIN ATT CONT
3. TUNE
4. FET ATT N
5. STC CONT
6. -12V
7, 9. GND
8. +5V
10. +12V
11. TEST ENABLE
12. TEST SIG
Q1
IF IN (60MHz)
[J824]
FET ATT N
PIN ATT
MIC
U25
[J825-5]
D-MONI-IN
(0 - 120mVdc)
[J825-7]
TUNNING
[J825-1]
IF signals of 60 MHz from the MIC are separated into the tuning amplifier Q7, 8 and
the IF amplifier on the Q1 side. IF signals are separated at U22 to the video detection
circuit on U3 side and the 60 MHz semi-log amplifier on T5 side. Respective outputs
video signals and 60 MHz IF signals are superimposed and sent to RPU-013. At the
input stage of SPU board, superimposed signals are separated at HPF and LPF.
Major control signals of IF board
- SDATA, CLK, DATEN, TEST SIG, TEST SIG ENABLE
SDATA, CLK and DATEN control signals from the RFC board control the gain of
U16. This control data is based on the setting value of [Menu] -> 0 -> 2 -> 2:Cable
ATT ADJ.
Purpose of the gain control;
Superimposed 60 MHz IF signals and video signals are sent to RPU-013 trough
the coaxial cable. IF signals of 60 MHz, in particular, inputted into RPU-013
have different levels according to cable length. The gain control is performed to
compensate the cable loss on the IF board side and allows inputs into RPU-013
at a constant level.
See page.4-13 for the adjusting method.
For TEST SIG and TEST SIG ENABLE control signals, dummy echo signals
are inputted into CR10 if [Menu] -> 0 -> 2 -> 2:Cable ATT ADJ is set to AUTO.
The gain correction is automatically performed based on these signals.
Hi: Disale
Lo: Enable
Q7,8 BPF
TUNE GAIN
S
M, L
FET ATT N
FET ATT N
PEDES TAL FET
Q3
U20 U21
CR10
Q2
TES T
TES T ENAB LE
PIN ATT CONT
ATT CONT
TUNE
Fig. 7.2.9 Block Diagram of IF board
TUNE GATE N
U6
CR2
U4
(DET)
Hi: SW ON
Lo: SW OFF
U23
S AMPLE HO LD
VBW A, B
TP1
U3
LOG
T5
Q4 U22
MBS ENAB LE
STC CONT
U25
ATT CONT
U18
7-14
7.2 Antenna Unit
TUNE IND
U5 U5
C28
U10
(B.W)
U11
LPF
STC DETECT
U16
U27 U28
HPF
VGA
SDATA
CLK
DATEN
SIG level
cable ATT ADJ.
D-MONI-OUT
(0 - 2.5Vdc)
Video SIG.
IF-VIDEO MIX
[J823]
(0 - 3Vdc)
To RPU-013
60MHz IF SIG.