Setup and Programming, (cont) / Operation 9
QAM MODE: This menu allows the user to set the modula-
tion type for the output. Choices range from QAM-16A
through QAM-1024B. 'A' suffixes indicate DVB compliant
FEC and the B suffixes indicate DigiCipher II FEC encod-
ing. Note that the output QAM mode usually must be
QAM-256. For CATV systems using DigiCipher II, select
the QAM-256B mode. For DISH Network QAM distribution
or other DVB systems using DVB set tops, choose the
QAM-256A mode.
GRAY ENCODING: This menu is only available when QAM
modes QAM-16A through QAM-1024A, are selected. The
choices are DVB and DAVIC. DVB is normally used for
video.
QAM SYMRATE: This menu allows selection of the output
QAM baudrate or symbol rate. Set as required by the set
top box.
If PRESET is selected, the symbol rate will be set accord-
ing to the QAM mode that has been selected. If MANUAL is
selected, pressing the right or left arrow buttons will allow
selection of symrates from 1.000 thru 7.000 MSym/Sec.
OUTPUT FORMAT: For normal operation, select NORMAL.
For system level set up, choose CW to provide a CW
carrier at the center frequency of the output channel for
use in leveling a system when a QAM power meter is not
available. In the CW mode, the CW carrier can be
measured on a spectrum analyzer without a need to apply
a bandwidth correction or it can be measured with an
analog meter tuned to channel center. The CW power
measured will equal the channel QAM power when the
modulator is returned to NORMAL output mode. Usually
OUTPUT CHANMAP, OUTPUT CHANNEL: Select the
desired EIA CATV channel output using these two menus.
RF LEVEL: Select the desired RF output signal level. The
available range is b30 dBmV and +42 dBmV,
selectable in 0.5 dB steps. The output accuracy is ± 1 dB.
OPERATION
MULTIPLEXING SIX INPUTS
To use the MQM6000L to multiplex six inputs, proceed as
follows:
1) Connect the six MPEG2 SPTS or MPTS signal
sources to the six ASI input connectors on the rear of
the MQM6000L.
2) Plug the power cord from the unit into the power
source.
3) Follow the instructions in the previous programming
section to select the desired MPEG programs. (See the
previous section for details.)
4) In the OUTPUT CHANMAP menu, select the output
channel format (BROADCAST, CATV, HRC, or IRC).
5) From the OUTPUT CHANNEL menu, select the
desired output channel number.
6) From the RF LEVEL menu, select the desired output
level. Depending on the diagnostic equipment avail-
able, you may want to select CW from the OUTPUT
FORMAT menu to balance the output with the outputs
of the other inputs to the cable system. When finished
balancing the system, select NORMAL from this menu.
7) From the QAM MODE menu, set the QAM modulator
to QAM-256B for use in a DigiCipher II environment. If
DVB, use QAM-256A instead.
8) In the QAM SYMRATE menu, select PRESET.
9) Set the OUTPUT FORMAT to NORMAL if you have
not already done so.
QAM signals are normally set 5 dB to 10 dB below analog
NTSC channels when balancing a system.
PRBS menu entries are used for testing purposes only
and should normally not be selected by the user.
