DG-OHM
UNAOHM Srl Rev. 4.0
16
9.2 OPTIMISATION (phase 2
button
)
Once the first phase of pointing to maximum power has been performed, now we have to
carry out a second step to optimise the quality. In fact, for digital signals, we do not always
improve the quality with quantity; this is why we carry out pointing for the quantity and
then, later, optimisation for quality.
Press the
button to activate the COFDM board, which will perform BER, MER, etc.
quality measurements. In this phase, we will have to make small movements on the
antenna to find the position that guarantees the best BER, MER and NM.
Digital signal quality is highlighted not only in numbers (ex. 1 e- 5, meaning error out of
100,000 symbols), but also through the quality bar image which will get longer as quality
improves, or which will become shorter as quality gets worse, until the signal is so
degraded in quality that it will give the "NO CARR" or UNLOCKED" message, or the
complete absence of quality.
In addition, the quality measurement bars can light up three different colours to give an
immediate idea of the quality:
GREEN
optimal condition of errors (few)
YELLOW
fair condition / some errors
RED
critical condition of errors
Once signal quality has been optimised, our quantity may have decreased, but this will not
influence our situation negatively.
Picture of the terrestrial digital screen button.
LOCKED:
SIGNAL LOCKED ON
UNLOCKED / NO CARR:
SIGNAL NOT LOCKED ON : due to poor quality or absence of
signal, no TV pictures can be seen.
Ch BER:
BER channel measurement (bit error ratio, or rather the number of
bit errors over time).
Pv BER:
Post Viterbi BER measurement (bit errors over time after the
correction of Viterbi).
MER:
Modulation error ratio (errors on modulation)
NM:
Noise Margin (guarantee margin in dB).
CELL:
Recognition code of the repeater from which the signal is being
received.
RU:
Uncorrected errors.
