BE-3110
26
4.8 Adjusting the Compression
Rate and Compression
Distortion of the IFv
(Refer to Fig. 4-11 adjustment
waveform diagram 1)
Note 10 :
Be sure to adjust according to the following order.
Note 11 :
As there are two modes for the compression rate;6 dB
and 10 dB, adjust in each mode.
1. Connect the devices as shown in Connection Diagram 6.
2. Set the devices as follows.
¶
Audio analyzer
1 kHz
¶
CATV terminal
US-7ch/10 dBmV input
¶
TV modulator
Fa: Adjust to ± 25 kHz
Fv: Modulation rate 87.5%
IFa: 41.25 MHz/45 dBmV
IFv: 45.75 MHz/50 dBmV
¶
Variable resistance attenuator
Adjust the output level to 10 dBmV
¶
Video SG
Staircase wave
¶
CW generator
100.15 MHz/60 dBmV/75
Ω
3. Tune the CATV terminal, and set this unit to the 6 dB mode.
4. Observe the S/N ratio using the audio analyzer.
5. Adjust the trimmer capacitor TC2 (CV2) of the RF ASSY so
that the value in step 4 becomes optimum.
6. Connect the devices as shown in Connection Diagram 7, and set
the devices as follows.
¶
Spectrum analyzer
0.2 dB/div
VBW: 1 MHz/RBW: 1 MHz
SPAN: 1 MHz
SWEEP TIME: 200 ms
f
0
: TV modulator Fv output
frequency
¶
Variable resistance attenuator
6 dB
Fig. 4-10 Connection Diagram 7
7. Disconnect the cables connected to IFa in and IFa out of the
unit.
8. Adjust the spectrum analyzer so that the compression modulation
peak level can be seen clearly on the spectrum analyzer screen.
(Use this item as the reference level.)
9. Set the variable resistance attenuator to 0 dB.
10. Adjust control VR2 (RV2) of the RF ASSY so that the bottom
level in the compression modulation of the signal comes to the
position set in step 7.
11. Connect the devices as shown in Connection Diagram 6.
12. Set the devices as follows.
¶
Audio analyzer
1 kHz
¶
CATV terminal
US-7ch/10 dBmV input
¶
TV modulator
Fa: Adjust to ± 25 kHz
Fv: Modulation rate 87.5%
IFa: 41.25 MHz/45 dBmV
IFv: 45.75 MHz/50 dBmV
¶
Variable resistance attenuator
Adjust the output level to 10 dBmV
¶
Video SG
Staircase wave
¶
CW generator
100.15 MHz/60 dBmV/75
Ω
13. Tune the CATV terminal, and set this unit to the 10 dB mode.
14. Observe the S/N ratio using the audio analyzer.
15. Adjust the trimmer capacitor TC1 (CV1) of the RF ASSY so
that the value in step 4 becomes optimum.
16. Connect the devices as shown in Connection Diagram 7, and set
the devices as follows.
¶
Spectrum analyzer
0.2 dB/div
VBW: 1 MHz/RBW: 1 MHz
SPAN: 1 MHz
SWEEP TIME: 200 ms
f
0
: TV modulator Fv output
frequency
¶
Variable resistance attenuator
10 dB
Spectrum
analyzer
115K
TV modulator
BE-3110
Variable
resistance
attenuator
Video
SG
Video in
RF out
Staircase wave
IFv out
IFa out
IFv in
IFa in
IFv in
IFa in
IFv out
IFa out
