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1.9
Selecting the COFDM mode
The COFDM mode of the output signal is selected using the “<” and “>” buttons.
Main menu
A
1236
MHz
TP
27.500
MS/s
3/4
QPSK
Outp.
S21
306.00
MHz
8
MHz
QAM64
!
Use the “+” or “-” keys to set the modulation type of the COFDM carriers to the values QPSK, QAM16, or QAM64 de
fi
ned in the
DVB-T speci
fi
cation.
Note:
Since the possible output data rate for COFDM-modulated signals is normally lower than the input data rate,
it is recommended to use the highest QAM stage (QAM64) if possible. The lower QAM stages QAM16 and
QPSK offer a higher resistance to interference but a lower data rate can be transmitted. The exclamation
mark beside the selected QAM stage indicates that the maximum possible output data rate is lower
than the input data rate. In this case the channel
fi
lter must be used and the number of channels limited
in the output data stream (see Chapter 1.12).
For the relationship between modulation type, code rate, guard interval and possible maximum data rate,
see Table 1 in Chapter 3.1.
1.10
Selecting the operating mode for the COFDM
modulator
In the
sub-menu of the COFDM mode
you can select the
operating mode (source signal)
for the COFDM modulator.
Press the “Sub-menu” button
to activate the sub-menu; press the “Sub-menu” button
again to deactivate it.
The modes are selected using the “<” and “>” buttons and adjusted using the “+” and “-” buttons.
Main menu
A
1236
MHz
TP
27.500
MS/s
3/4
QPSK
Outp.
S21
306.00
MHz
8
MHz
QAM64
!
“COFDM modes” sub-menu
***
UFO331TP
***
Mode
SAT Sig
Guard
1/32
Code rate
5/6
The following settings are available:
Mode
SAT Sig
Normal mode,
the SAT input signal is transmodulated, in the case of input signal interference only full bytes (0xFF)
are
modulated
PRBS
Test mode: the COFDM signal is modulated with a PRBS-23 sequence, normal mode is not available
in
this
setting
CW
Test mode: sine wave signal for levelling using simple measurement devices, normal mode is not
available
in
this
setting
Main menu (display in PRBS mode)
PRBS
Outp.
S21
306.00
MHz
8
MHz
QAM64
!
“COFDM mode” sub-menu (for setting the PRBS)
***
UFO331TP
***
Mode
PRBS
Guard
1/32
Code rate
5/6
Содержание 20610100
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