R&S FSL Cable TV Measurements (Option K20)
1300.2519.12 2.59 E-11
C/N Quiet Line measurement
Test setup:
Refer to the section Analog TV test setup.
Procedure:
1. Press the SWEEP key.
2. Press the Single Sweep softkey.
3. Press the FREQ key.
4. Enter 210.25 MHz for the vision carrier frequency of the input signal.
5. Press the MEAS key.
6. Press the Analog TV softkey.
7. Press the C/N softkey.
8. To change the limits, press the Edit Table softkey.
9. To adjust the input attenuator, press the Adjust Attenuation softkey.
10. Press the C/N Setup softkey to open the C/N Setup dialog box.
Make sure, that Quiet Line is chosen as measurement mode.
Set the Reference Noise Bandwidth to 5 MHz (or another value).
If desired, activate the Noise Floor Correction option.
11. Press the RUN key.
The R&S FSL will first measures the carrier power. This is not visible on the screen. In contrast to
the Off–Service mode, the R&S FSL will not ask you to turn off the signal in the measurement
channel. The noise spectrum is measured by a gated FFT.
Note: The active modulation standard contains a Quiet Line parameter. It tells, in which video line the
vision carrier is not modulated. Be sure to set this parameter correctly (for details refer to
Modulation standards)! The R&S FSL captures IQ data during this line and calculates an FFT.
The result is shown in the upper pane as noise measurement trace.
You do not have to choose the noise measurement frequency by moving a marker like in the Off–
Service mode, instead the R&S FSL automatically calculates the mean noise power. Measurement
values close to any typical CSO beat frequency are omitted in this process (vision carrier and vision
carrier ± n* 0.25 MHz).
This automatically calculated average noise level is translated to the reference noise bandwidth you
specified in step 10.
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