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Chapter 06 – Measuring range 21
10911 V01.10
Note:
The measured values from the measuring receiver are calibrated with AFC switched on. Therefore, the
AFC should only be switched off in order to check for a frequency offset.
The AFC of the receiver can be switched on and off using the menu
MODE> AFC
and it is always activated after
stopping the measurement using
ESC
.
6.2.5 BER measurement (bit erroe rate measurement)
As mentioned in the previous section, the BER measurement result is displayed in the BER window. The measuring
receiver can measure the bit error rate before Viterbi (CBER) and after Viterbi (VBER) simultaneously. VBER is displayed
in a smaller font on the top line of the BER window. CBER is below in a large font.
6.2.6 MER measurement
The MER value of the signal in the baseband (after the demodulator) is displayed in dB in the MER window. The measu-
ring range is between 2.0 and 20.0 dB. The resolution is 0.1 dB.
6.2.7 Noise Margin (NM)
For “white noise” a minimum limit for the signal quality where no error occurs (QEF) can be defined.
The margin of the MER to this limit is the noise margin (NM). That value is displayed in the MER-window in dB with a
resolution of 0.1 dB.
To simplify the decision if the signal is good, NM is colored green, yellow if it’s less optimal or red if it’s bad. The limits of
the VBER (> 2e
-4
is bad and <1e
-6
is good) also contributes to this decision.
The following table shows minimum signal quality in relation to the FEC.
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