Promax HD Ranger +, Руководство пользователя

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2 December 2014
DVB-T Measurements
Power
Measured power over the entire bandwidth of the channel.
C/N
Carrier/Noise ratio, where C is the received power of the modulated
carrier signal and N is the received noise power. To measure it correctly
the channel should be tuned at its centre frequency.
MER
Modulation error ratio with link margin (LM). The link margin indicates the
safety margin respect to the MER level, measured for the degradation of
the signal up to the QEF (Quasi Error Free) value. MER represents the
ratio between the average power of the DVB signal and the average noise
power of the signal constellation.
BER (VBER/CBER)
It is the system error rate. In a system of digital terrestrial signal
reception, after the COFDM decoder two methods of error correction are
applied. Each time an error correction is applied on the digital signal, the
error rate changes, so if the error rate is measured at the demodulator
output or after Viterbi or at the Reed-Solomon decoder output, different
error rates are obtained.
CBER
BER measurement for digital signal before the error correction (BER
before FEC).
VBER
BER measurement for digital signal after error correction (BER after
Viterbi).
In order to have a reference about the image quality, it is considered that
a system has good quality when it produces less than one un correctable
error per hour of transmission. This border is called QEF (Quasi-English
Error-Free,) and corresponds to one error rate after Viterbi equal to
2x10E-4, or 2 bit errors per 10.000.
This value is marked on the BER measurement bar after Viterbi. This the
BER for acceptable signals should be to the left of this mark.
PER
Measurement associated to VBER. It is an errored packet counter, plus a
total time counter, accounting for total packets lost over a given period of
time.