DRAKE TMQAMasi 매뉴얼 - 페이지 3

{카테고리_이름} DRAKE TMQAMasi에 대한 매뉴얼을 온라인으로 검색하거나 PDF를 다운로드하세요. DRAKE TMQAMasi 4 페이지. Digital qam modulators

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CHART OF DISPLAY MENUS

The following chart shows all choices that are

available for each parameter.

The following information may serve as an aid in

setting up the TMQAM parameters.

Use the procedure on page 4 to enter the adjust

mode. Select the SOURCE menu. Normally, the

EXTERNAL selection would be used to select the

MPEG2 transport stream input. The PRBS

selections provide test sequences generated

inside the TMQAM and are for testing the

modulator without a MPEG2 input source.

Advance to the next menu using the left or right

arrow buttons. Continue this process until all

parameters have been checked and/or adjusted.

Press the ENTER button to load and store all

adjusted parameters. The ENTER button can be

used after each parameter adjustment or, if

desired, wait until all parameter adjustments are

set and then "ENTER" adjustments all at once.

The INPUT menu is used to select an inverted

clock if this is required. Usually the NORM

selection for normal clock will be required. Select

INV if an inverted clock is used.

The OUTPUT menu is used to select the output

mode. The CW setting is for testing and should be

selected to allow setting of the upconverter output

level using a device such as a signal level meter

or spectrum analyzer. For normal operation, one

of the MOD settings is required. If the output

upconverter uses high side local oscillator

injection and inverts the output spectrum of the

TMQAM (the Drake DUC upconverters do this),

select the MOD-INV setting to provide a normal

output from the upconverter. If the upconverter

does not invert the spectrum or if you are use the

44 MHz IF output directly, you may need to select

the MOD-NORM setting.

The LOOP BW menu is used to adjust the loop

bandwidth of the input tracking loop. Use 20 Hz as

a default setting. In some cases, this may need to

be changed – 100 Hz if the signal is very jittery or

1 Hz if stable and weak. 20 Hz or 10 Hz are

usually best for most sources.

The MODE menu is used to select the desired

forward error correction mode. This must match

that of the demodulating device (set top box, etc).

Select ITU-A for DVB applications or select ITU-B

for DigiCipher II® applications.

The ENCODER menu is used only if ITU-A was

set as a mode. Select DVB or DAVIC mapping as

required.

The QAM menu is used to select the QAM order

desired. 16QAM, 32, 64, 128, or 256QAM may be

selected in the ITU-A mode.

SETUP PROCEDURES

Most CATV systems are using 64QAM or

256QAM for digital video. In the ITU-B mode, the

only choices are 64QAM or 256QAM.

The ALPHA menu displays the roll-off setting for

the baseband filtering. ITU-A is 15% and ITU-B is

18% excess bandwidth. THESE CANNOT BE

CHANGED.

The INTERLV menu allows setting of the

interleaver values. The ITU-A setting is fixed at

I=12, J=17. The ITU-B mode allows many

combinations. The required setting should be

specified by the system designer. If the demodu-

lating device must have a particular set of values,

then select the appropriate matching setting. For

ITU-B, many systems use I128, J4 or I128, J1.

The CLOCK menu allows selection of the clock

mode of operation. If AUTO is selected, the output

baud or symbol rate will automatically track that of

the input stream. If FIXED is selected, the output

rate will remain fixed at this setting and the

TMQAM will add null packets where required if

the input rate is slower. If the input rate exceeds

the fixed manual setting, an error will result.

Some set top boxes are designed to operate at

only one fixed symbol rate. If this is the case for

your installation, use FIXED setting and set the

value in the next menu to match that of the set top

box. Advance one menu with the right arrow. This

BD RATE menu will display the output symbol

rate. If a fixed setting is required, use the BD

RATE page to make the selection.

The BD RATE menu displays the current output

symbol rate or baud rate. If the FIXED option has

been selected for the clock, use this menu to

adjust the output rate to the desired rate. When

timed out from the set up process or adjust mode,

the BD RATE page will be the default display

menu. If the Auto Clock selection has been

made, this menu will be skipped in the adjust

mode. You can check bit rate or firmware version

using the procedure described below.

DEFAULT DISPLAY /FIRMWARE REVISION / BIT

RATE: After making and saving the above

adjustments, the display will time out and default

to the BD RATE screen showing the output baud

rate or symbol rate. When this menu is being

displayed and you are not in the adjust mode,

pressing the up arrow will display the firmware

revision number. If the down arrow is pressed, the

display will display the data bit rate. Press the

down arrow button again to go back to displaying

the output baud rate.