CATV Measurements
5–38
2715 User Manual
When the DESIRED-to-UNDESIRED measurement is initiated, the 2715
performs the following:
1. Average power measurements as is done as described in the CARRIER
LEVEL -- AVG POWER menu on page 5–23.
2. The user is prompted to turn the channel under test off.
3. Then the Resolution Bandwidth is set to 30 kHz and the Video Bandwidth to
30 Hz.
4. A sweep is initiated.
5. Any coherent distortion signals are identified and the value of the most
powerful one is recorded.
6. The power spectral density of all screen locations is integrated between the
edges of the channel and is calculated.
NOTE
. A correction for the instrument noise floor is made and the power in any
signals found in step 5 is included in this calculation.
7. The results of the calculation done in step 6 is stored as a desired-to-
undesired ratio. The frequency limits that the power was measured within are
stored as the signal bandwidth. The largest coherent signal found in the
undesired measurement is also reported, but not stored.
The following procedure shows how to make a CARRIER-TO-NOISE or
DESIRED-to-UNDESIRED measurement:
1. Press [CATV/APPL] to call up the CATV MEASUREMENTS menu. See
Figure 5–1.
2. Press [5] to select the CARR/NOISE -- DESIRED/UNDESIRED measure-
ment menu.
This displays the following options:
0
RUN C/N -- D/U
1
STORE CURRENT RESULTS
2
DISPLAY RESULTS
3
PRINT CURRENT RESULTS (RS-232 Only)
4
PRINT STORED RESULTS (RS-232 Only)
5
SET UP CARRIER/NOISE
7
IN-SERVICE
9
LEAVE C/N -- D/U
3. Press [7] to toggle between normal or in-service basis.
DESIRED-to-UNDESIRED
Enable CARR/NOISE --
DESIRED/UNDESIRED
Measurement
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