axing MK 16-00, Руководство по эксплуатации

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2021-08-01 | Technical improvements, changes in design, printing- and other errors reserved. 37
DVB-T guard interval: A guard interval is transmitted between the symbols of the useful signal.
This guard interval avoids the intersymbol interference during the DVB-T
transmission.
The delayed signals of other synchronized DVB-T senders or reflections have no
effects on the decoding of the useful signal if they arrive during the guard
interval. The period of the echoes must be shorter than the duration of the
guard interval.
Changing the guard interval adjusts the ratio between the transmission
duration of the useful symbols and the duration of the guard interval.
A great guard interval (e.g. 1/4) leads to a really small data rate.
When transmitting on a perfect coaxial distribution network, a really small
guard interval (1/32) is enough.
DVB-T transmission
modes (2 k and 8 k):
Using the 8 k mode is recommended for reflections with really long durations.
Due to the long symbol duration, long guard intervals are possible.
Fine Level: The Fine Level option include fine attenuation from 0 to -3dB of each
modulator output and the deactivation of the modulator (off).
Fine Tune: The fine Tuning of the output channel is performed in 1 MHz steps.
4.4.2. Fill level
The data rate of the sender may vary depending on the image contents and on the transmission quality. To
ensure an undisturbed reception, a reserve must absolutely be observed.
We recommend you to set the maximal fill level to 90%.
If the current fill level exceeds the maximal fill level, it may cause image disturbances, e.g. mosaic images.
If the net data rate of the signal exceeds the net data rate of the output channel, the modulator overflows. This
overflow leads to disturbances. If the modulator overflows, the status LED on the front side of the device lights
in red.
Filtering the programs reduces the net data rate of the input signal. Subsequently, the net data rate of the
output signal is also reduced.
The data rate of the DVB-T channel depends furthermore on the chosen channel bandwidth (7 or 8 MHz), on
the set error correction rate (FEC) and the modulation rate (QPSK, QAM16, QAM64) of the modulator.
If the displayed data rate exceeds 90%, there are different possibilities to change it:
è
Change to a channel with a bandwidth of 8 MHz if a 7 MHz channel was selected previously.
è
Raise the modulation rate to 64 QAM. QPSK corresponds to the lowest, the QAM64 setting to the highest
output data rate.
è
Set the forward error correction to 7/8. With this setting, the data rate is increased, but the error
correction is lower. A lower error correction requires a better transmission quality from the antenna
network.
è
Set the guard interval to 1/32. This shorter guard interval allows you to reach greater data rates.
è
Reduce the number of selected programs in the channel list.