R&S FSL Cable TV Measurements (Option K20)
1300.2519.12 2.53 E-11
6. Press the Line softkey to enter the line number.
7. To change the sweep time, press the Sweeptime Manual softkey and enter a value (25Rs up to
100 Rs).
8. To define a trigger offset, press the Trigger Offset softkey and enter a value (–50 Rs up to 50 Rs).
C
hoose 0 Rs to make the display start with the horizontal sync of the specified line. Negative values
make the display start earlier.
9. To adjust the input attenuator, press the Adjust Attenuation softkey.
10. Press the FREQ key.
11. Enter 210.25 MHz for the vision carrier frequency of the input signal.
12. Press the RUN key.
The trace shows the luminance signal during the selected period versus time. The group delay is
not compensated internally.
Fig. 2-35 Video Scope measurement
Vision Modulation measurement
This measurement determines the "residual picture carrier'' and the modulation depth of the vision
carrier.
The vision carrier is amplitude modulated (AM). To be more precise, it uses the residual sideband
amplitude modulation. Most standards use negative amplitude modulation. Therefore, the vision carrier
has its highest level when the luminance signal is equal to the "synchronizing level''. And it has its
lowest level when the luminance signal is equal to the "peak white level''. The "synchronizing level'' can
be measured in every horizontal synchronizing pulse. The "peak white level'' can be measured in
special test lines ("bar line"), where a white reference is transmitted.
The residual picture carrier is the ratio of the "peak white level" to the "synchronizing level". The sum of
the vision carrier's modulation depth and the residual picture carrier value must equal 1.
The measurement display is split into two panes. In the upper pane, the RF level of the vision carrier
during one horizontal line is displayed. In the lower pane, the result table for the measurement is
displayed.
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