Chapter 20 - Upstream monitoring system UMS 141
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20.4.2
Wobbling (Frequency Response Measurement)
This measurement determines the frequency response in the return channel range. The handheld
transmits a constant level over the total frequency range, the frequency response received at the
headend is shown in graphic form in the display.
Selection with the function key
WOBBEL
of the UMS main menu. The wobbling measurement can
be left again by pressing the function key
BACK
(if the function keys are not shown, press any
key).
Figure 20-2 UMS frequency response measurement
20.4.3
MER/BER measurements, constellation diagram
These measurements permit a qualitative assessment of the channel quality. The measuring
instrument sends a PRBS modulated signal in a predefined (by the headend) frequency range
which will be measured in the headend as to Modulation Error Rate (MER) and Bit Error Rate
(BER). The measurement results will be shown in real time on the display.
Selection with the function key
MER/BER
from the UMS main menu. The MER/BER measurement
can be left again by pressing the function key
BACK
. You can choose between four measurements
(in set frequency ranges) which are marked as
MEASURE1
,
MEASURE2
,
MEASURE3
and
MEASURE4
.This corresponds to the stored measurement parameters in the headend. Ongoing
measurements can be stopped again by the function key
BACK
. If a measurement is active, the
constellation diagram obtained can also be shown by pressing the function key
CONST
. This
diagram can be closed again by pressing the function key
CONST
again.
20.4.4
TILT measurement / Line-up
The TILT measurement serves for an easy line-up of amplifiers (in the line as well as house
installation amplifiers). Selection by the function key
LINE-UP
of the UMS main menu. The TILT
measurement can be left again by pressing the function key
BACK
.