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Chapter 6 - TV Measuring Range
10713 Vxx.11
The BER is shown on the display in exponential form.
The measuring depth can be shifted between 1•10
8
and 1•10
9
bits. For changing the measuring
depth at first the key
HOME
has to be pressed. Then the depth of the bit error rate measurement
can be set to 1•10
9
(1 billion) bits via the menu item
BER -> e-9
.
Via the menu item
e-8
the measuring depth can be set back to the default setting 1•10
8
. This
setting is non-volatile. In the operating mode DATAGRABBER and DATALOGGER the
measurement of the bit error rate generally operates with a depth of 1•10
8
bits.
MER measurement (Modulation Error Rate)
6.2.2.2.4
In addition to measurement of the bit error rate, it is established practice within digital transmission
also measures the MER. It is defined in ETR290. MER is calculated from the constellation points.
It is the counterpart to S/N measurement with analog transmission methods. The measuring range
goes up to 40 dB with a resolution of 0.1 dB.
Noise Margin (NM)
6.2.2.2.5
In case of white noise a limit value of MER for the minimum signal quality (QEF) can be determined
which depends on the modulation.
The difference of MER to this limit value corresponds to the system reserve NM (noise margin).
Just as MER it is displayed in dB with a resolution of 0.1 dB. For an easier assessment of the
signal quality the NM is shown in the colors red for bad, yellow for limited and green for good signal
quality. The limit values for the BER (>2e-4 for bad and <1e-6 for good) will also be included in this
assessment.
PE measurement (Packet Error)
6.2.2.2.6
Short interruptions in the DOCSIS signal usually cannot be detected using MER and BER
measurement. They can make entire packets in the transport stream unusable, however. The
measuring receiver has a function with which corrupt transport stream packets are summed from
the point in time of entry of a new channel.
The number of packet errors (PE = Packet Error) and the amount of time that has passed since the
last tuning process is displayed.
Constellation diagram
6.2.2.2.7
The constellation diagram can be called via the menu item
CONST
, if the measurement receiver is
tuned. For further information see Chapter 13 - Constellation diagram.
