TMQAM
asi
ENTER
QAM
MODULATOR
BIT RATE
19.327 M
FRONT PANEL CONTROLS AND INDICATORS 2
F1
F2
F3
Figure 1
F4
F3
F4
F3 -
Left and Right Button
Use the Left and Right buttons to select the
parameter you desire to view or adjust.
F4 -
Up and Down Buttons
Use the Up and Down buttons to adjust a
parameter value when in the adjust mode.
When not in the adjust mode, the UP button
displays the version number. The Down button
displays the incoming bit rate if the "AUTO"
clock mode has been selected.
F1 - LCD Display
Displays the modulator parameter and its
setting.
F2 -
ENTER
ENTER
Use the ENTER button to enter the adjust
mode or to save and load a new parameter
value. Hold for 2 seconds to enter the adjust
mode. After adjustment, press this button once
to load and save the value.
1 TMQAM and TMQAMasi DIGITAL QAM MODULATORS
TM
TMQAM
asi
ENTER
QAM
MODULATOR
BIT RATE
19.327 M
GAIN
DUC550
POWER
ERROR
3
5
TMQAM
ENTER
QAM
MODULATOR
BIT RATE
19.327 M
CATV
CATV+100
GAIN
DUC860
POWER
ERROR
3
5
TMQAM
asi
ENTER
QAM
MODULATOR
BIT RATE
19.327 M
GAIN
DUC550
POWER
ERROR
3
5
TMQAM
ENTER
QAM
MODULATOR
BIT RATE
19.327 M
CATV
CATV+100
GAIN
DUC860
POWER
ERROR
3
5
POWER SUPPLY
PS8
12 POSITION RACK MOUNT POWER SUPPLY
TMQAM MODULATOR
Thus the output symbol rate can change if the
input data rate changes. The TMQAM
asi model
does not have an "Auto" selection. In the
‘Fixed’ mode, the desired output symbol rate is
programmed from the front panel. This rate
must be equal to or greater than the incoming
data rate. The output rate will be maintained at
the set rate and if the input rate is slower than
this rate, the TMQAM and TMQAM
asi will add
null packets to make up for the slower
input rate.
The modulators have several test modes that
can be selected. In these modes, a
pseudo-random binary sequence stream is
substituted for the input source. This will
provide a modulated output without any
external input source.
A CW output mode is selectable to allow
measurement of the output level with an analog
signal meter.
The RF output is +30 dBmV. This IF output
can be connected to one of the DRAKE DUC
series of digital upconverters to provide an
output on a CATV or broadcast channel.
The R.L. Drake model TMQAM and TMQAM
asi
modulators are professional quality modular
digital headend components designed to
provide optimum performance with minimized
rack space requirements. These modulators
accept an MPEG2 transport stream input in
either the SPI format or ASI serial format,
depending on the model, and is capable of
providing a QAM output with 16, 32, 64, 128,
or 256 constellation points.
The modulators perform the forward error
correction (FEC) encoding according to ITU
J.83 Annex A or Annex B. Annex A is referred
to as ‘DVB’ and Annex B is referred to as
‘DigiCipher II®’. The front panel push-buttons
and display provide full access to many other
parameters that can be set to match a
particular application.
The TMQAM model provides a choice of two
clock modes. In the ‘Auto’ mode, the output
clock rate is automatically locked to the
incoming data clock rate.
TMQAM
asi MODULATOR
