DVB-T transmission
modes
2k fix
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.
•
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 programmes 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, 16QAM, 64QAM) of the modulator.
If the displayed data rate exceeds 90%, there are different possibilities to change it:
•
Change to a channel with a bandwidth of 8 MHz if a 7 MHz channel was selected previously.
•
Raise the modulation rate to 64QAM. QPSK corresponds to the lowest, the 64QAM setting to the highest output data
rate.
•
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.
•
Set the guard interval to 1/32. This shorter guard interval allows you to reach greater data rates.
•
Reduce the number of selected programmes in the channel list.
COFDM modulated channels allow net data rates from 4.98 up to 31.67 Mbit/s (typically 24).
Modulation
Code rate
Guard interval
1/4
1/8
1/16
1/32
QPSK
1/2
4.976
5.529
5.855
6.032
2/3
6.635
7.373
7.806
8.043
3/4
7.465
8.294
8.782
9.048
5/6
8.294
9.216
9.758
10.053
7/8
8.709
9.676
10.246
10.556
16-QAM
1/2
9.953
11.059
11.709
12.064
2/3
13.271
14.745
15.612
16.086
