Operation instructions | Serie RFQ-845 and Serie RFO-845
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.
Output level:
The
Output Level
options include attenuation and deactivation of the
modulator. The settings are separate for each of the four modulators. The
max. output level of approx. 105 dBµV is reached with an
Output Level
setting of 20 dB.
Vernier adjustment:
The vernier adjustment of the output channel is performed in 1 MHz steps.
3.5.2.
Fill level
The data rate of the sender on the DVB-S/S2 transponders 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 (see 3.4 on page 19) 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:
Change to a channel with a bandwidth of 8 MHz if a 7 MHz channel was selected previously.
Raise the modulation rate to 64 QAM. QPSK corresponds to the lowest, the QAM64 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 allow
s
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
3/4
14.929
16.588
17.564
18.096
5/6
16.588
18.431
19.516
20.107
7/8
17.418
19.353
20.491
21.112
64-QAM
1/2
14.929
16.588
17.564
18.096
2/3
19.906
22.118
23.419
24.128
3/4
22.394
24.882
26.346
27.144
5/6
24.882
27.647
29.273
30.16
242016-10-31 | Technical changes, design modifications, errors and misprints are subject to change without prior notice.
