936.2332
/E
/0905
/6
.1
6
e
6
Main menu
Submenu QAM stages
7. Selecting the modulation signal for the QAM modulator
The selection of the modulation signal for the QAM modulator is carried out in the submenu of the QAM ranges.
Access the submenu with the “
+
” or “
–
” key and make the desired setting.
Possible settings are :
●
“SAT-Sig”
Standard operation,
the Sat input signal is converted, no output signal during interruption of
the input signal
●
“SAT-PRBS”
Standard operation,
the Sat input signal is converted, output signal switches during interruption
of the input signal to PRBS-23 (output spectrum remains the same).
●
“PRBS”
Test signal PRBS-23. Independent from input signal.
Standard operation is not possible.
●
“CW-Mode”
Test signal
for levelling with simple measuring instruments.
Standard operation is not possible.
If the CW signal is switched on (only selectable in twin A), a sinusoidal carrier with 85 dBµV is generated
on both channel units (both twin A and twin B).
In the “PRBS” operating mode, the output symbol rate (e.g. 6.875 MS/s) can be set (see selection of the output symbol
rate in operation mode PRBS and Stuffing with and without programme filter).
Input
1568
MHz
27,500
MS/s
3/4
Output
S21
306,00 MHz
6,875
MS/s
64
QAM
***
UFO 386/TP
***
Modulation
SAT-Sig
Spectrum
normal
< Return:
Submenu >
Main menu for PRBS
Submenu QAM stages, PRBS setting
***
UFO 386/TP
***
Modulation
PRBS
Spectrum
normal
< Return:
Submenu >
PRBS
TP
Output
S21
306,00 MHz
6,875
MS/s
64
QAM
In the
“Sat-PRBS”
operation mode, the channel unit automatically transmits PRBS if the unit cannot lock on to the set Sat
signal. In this case, the previously set output symbol rate for
“PRBS”
or
“Stuffing”
is valid. If the output signal can be
modulated again, the channel unit switches back to transmodulation.
If the output symbol rate is to be set, it is necessary to choose the operation mode “PRBS” temporarily or to switch
to “Stuffing”. Setting to “Sat-PRBS” is not possible.
It is recommendable to set the output symbol rate to the same value as the automatically determined symbol rate for the
set transponder so that the output spectrum remains the same when switching over to PRBS.
While the channel unit transmits the PRBS replacement signal in the SAT-PRBS operating mode, the following will be
displayed on the control unit (the code rate is not displayed because the input has not locked in).
