DRAKE MQM6000L 사용 설명서 - 페이지 9

{카테고리_이름} DRAKE MQM6000L에 대한 사용 설명서을 온라인으로 검색하거나 PDF를 다운로드하세요. DRAKE MQM6000L 15 페이지. Multiplexing qam modulator

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Setup and Programming, (cont) / Operation

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

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.

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 between +30 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.