DRAKE MEQ1000A Buku Petunjuk - Halaman 6
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6 General Description
GENERAL DESCRIPTION
The R.L. Drake model MEQ1000A is a commercial grade
hybrid QAM modulator. The MEQ1000A features plug-in
input modules that include an ATSC/QAM tuner, an ASI
input, an SDI/HD-SDI input, HDMI (non-HDCP), Compo-
site input, Component input, and analog NTSC inputs;
thus the description 'hybrid' is used to describe it. A
multiplexer is built in to combine the transport streams
and input the filtered and groomed transport stream to
the QAM modulator. This manual includes feature ex-
amples utilizing the Drake DTD1000 Digital Tuner and
Demodulator Module, and the ASII ASI-Input Module.
Other available input modules include:
SDE24 Dual SD MPEG Encoder
HDE24 High Definiton MPEG Encoder
SDI24A SDI/HD-SDI Input Encoder
SDE24EAS Emergency Alert System Encoder
The MEQ1000A has two input module slots and the out-
puts interface to the MEQ1000A multiplexer, internally,
where they are MPEG program filtered, multiplexed, and
groomed. Programs, among the total group from input
module A and input module B, may be selected or not
selected by the operator to be sent to the QAM modula-
tor. Each input must contain no more than 20 programs
and a maximum of 20 programs per input may be select-
ed. Also, the total bitrate of the selected programs must
not exceed that of the output QAM channel capacity.
Some common applications include: Channel Drop/Add,
cherry picking programs from ASI MPTS inputs, digital
channel processing, or local origination additions.
The MEQ1000A contains a high performance QAM mod-
ulator that can operate in most ITU-A or ITU-B modes up
through 1024QAM. The very low noise, high output, up-
converter provides coverage from 54 MHz to 1002 MHz
while maintaining exceptionally low phase noise and
broadband noise. Output level can be selected at a val-
ue between + 45 dBmV and + 61 dBmV.
The MEQ1000A operates in a fixed output clock mode
and processes null packets when required to maintain the
set fixed clock rate. PCR correction is included.
DIGITAL CHANNEL PROCESSING (One input module)
The DTD1000 input module tunes any 8-VSB or QAM
channel between 54 MHz and 1002 MHz. It is ideal for
digital 'channel processing' applications where a single dig-
ital video signal is received, error corrected, clocked at a u-
ser determined fixed rate and remodulated on the same or
another RF channel. Applications include cleaning up a
low MER QAM signal received from a CATV source or fiber
shifting the RF frequency of a QAM
link receiver, or
QAM OUTPUT
0.000 Mbits/S
MEQ1000A MULTIPLEXING HYBRID QAM MODULATOR
modulated signal. It may be used to convert one off-air ATSC 8-
VSB signal to a QAM output with rate adjustment. Used in the
processor mode with only one input, the DQT1000 can process
ATSC or CATV QAM inputs. No multiplexing or altering of any
MPEG tables is performed in this mode.
Used in the non-multiplexing mode, the data rate of the incom-
ing signal can be any rate that falls within the specification
range. The output rate can be set to any fixed output rate (e-
qual to or faster than the input rate).
MULTIPLEXING TWO ATSC TRANSPORT STREAMS
Utilizing two DTD1000 input modules, two off-air 19.4 Mbps ATSC
signals (QAM modulated CATV delivered signals could also be
used) can be received and multiplexed to obtain a 38.8 Mbps
256QAM output. Thus two ATSC inputs can be output on a single
6 MHz bandwidth 256 QAM channel.
Another way of combining two ATSC 19.4 Mbps streams is to
receive the first stream using the 8VSB input (DTD1000) and
input the second stream, if available in ASI format, through the
ASII module in the second input slot. Again the two combined
ATSC signals will be modulated at 256QAM in a 6 MHz wide
channel. If it is desired to provide both ATSC signals from two
ASI sources, two ASII modules can be used.
When the MEQ1000A is used as described above, no loss of
picture or sound packets occurs. There is no added compression
of the video or audio streams. Only the necessary control packets
are rewritten to prevent duplication of MPEG2 program numbers
and major and minor channel number assignments in the tables.
Using a PC interface, the operator can select the major and minor
program numbers that he desires for each program in the output
multiplex.
PROGRAM FILTERING
A 'Select Program' function is provided to allow the operator to
select which of the MPEG programs present on the A and B input
streams are to be included in the output multiplex.
PSIP OPTIONS
When operating in the multiplex mode, the MEQ1000A can be set
to process PSIP information from both sources and rewrite tables
containing combined PSIP information, or in cases where the offair
broadcast channels may not be transmitting some or all of the
tables, it can be set to ignore and discard the PSIP tables
completely, or it can be set to generate MGT and VCT tables
without EIT tables. Null packet processing is applied as necessary
to keep the output data rate at the desired setting. PCR
correction is provided. The operator can program desired major
and minor channel numbers for each program in the output
stream.
OUTPUTS - RF and ASI
The 54 to 1000 MHz RF output is always QAM regardless of
whether the input is VSB or QAM. This same filtered stream is
also output via the rear panel ASI output jack.