5
General Description
the R. L. Drake® model aCt1000 is a commercial grade,
modular digital headend component providing 8VSB or
Qam input to Qam transmodulation and Rf upconversion
in a single unit. up to 10 aCt1000 modules, along with the
required PS151 power supply module, can be installed into
a single Rmt150 rack mounting tray, occupying only 2 rack
units (3.5''). the aCt1000 supports atSC 8VSB and itu
j.83 annex B 64Qam and 256Qam inputs, and outputs an
agile itu j.83 annex a or B Qam channel. the aCt1000
supports Rf inputs from 54-1002mHz from an antenna
or cable feed. the modulator supports Rf channels from
54-1002mHZ, and all annex a and annex B Qam modes up
to 256Qam, including all interleaver settings for annex B. the
transcoder demodulates the desired digital channel, adapts
the bitrate from the input to output if necessary, and modulates
the entire multiplex of programs on the output channel.
PCR values are recalculated as required when the input
and output bit rates are not identical, and channel display
numbers (PSiP and mGt/VCt table entries) can be changed.
Installation and Mounting
install the aCt1000 transcoders into the Rmt150 rack
frame. insert each aCt1000 into the frame until the ''f''
connector extends through the front panel hole, the LeD is
aligned with the opening in the front panel, and the hook-
shaped projection near the rear of the aCt1000 engages
the rear of the frame. Secure the module into the frame
with the supplied nylon washer and 1/2'' ''f'' connector nut.
Connect the supplied power supply cable between the
aCt1000 and the frame-mounted PS151, ensuring that
the correct power supply port is used for the frame slot
location (slot 1 is the left-most slot, as viewed from the front).
Connect the aCt1000's input signal source to the front-
panel ''f'' connector. Connect the rearmounted output ''f''
connector to the output combiner as required for the system
configuration. ensure that the PS151 is plugged into an aC
power source. When using the Rmt150 rack frame, it is not
necessary to leave vertical airspace between the frame and
other equipment in the rack, unless other equipment in the rack
specifies minimum gaps. the transcoders and power supply
are designed to provide sufficient cooling and airflow, even
when mounted with adjacent Rmt150 units above and below.
General Description/ Installation and Mounting/ Configuration
Configuration
the aCt1000 is controlled primarily via the Drake
model PS151 front-panel interface. the following menu
options are available for configuring the aCt1000
(menu name listed in bold, valid settings listed in italics:
· IN MODE: VSB-8, QAM-64B, QAM-256B – this configures
the input modulation mode that the aCt1000 will use
· IN PLAN: OTA, CATV, IRC, HRC – this selects the
channel plan for the receiver section (uS off-
air, uS standard cable, iRC, or HRC respectively)
· IN CHAN: 1-158 – this selects the input channel number;
the range varies depending upon the channel plan selected
· ENCODER: ITU-B, ITU-A – this selects the output modulator
Qam mode (itu j.83 annex B or annex a, respectively); for
uS cable applications, this should typically be set to itu-B
· MODULAT: 256-QAM, 128-QAM, 64-QAM, 32-QAM,
16-QAM – this selects the output modulator Qam density;
only 256- and 64-Qam modes are available in annex B
· INTERLV: All ITU interleave modes supported – this
allows the operator to choose a specific output interleave
mode, as necessary (annex a mode only supports one
interleave mode, as only one is specified in the standard)
· CLOCK: PRESET, MANUAL – when set to maNuaL the
output symbol rate is continuously variable via the next
setting; when set to PReSet the symbol rate is fixed at
the appropriate bitrate for the modulation mode chosen
· BD RATE: 1.0000-7.0000 Ms/s – when the previous
setting is configured for maNuaL, this allows the output
symbol rate to be configured to an arbitrary symbol
rate. Note that some higher-bitrate symbol rates may
occupy more than 6mHz channel bandwidth, and that
very-low-bitrate symbol rates will not fill a 6mHz channel
· OUTPUT: NORMAL, STANDBY, CW – changes the
output mode to StaNDBy (no output) or CW (a CW
pilot with the correct output power) from NoRmaL
·
RF OUT: 29.5-45.0dBmV – sets the
output power level of the modulator
· CH PLAN: OTA, CATV, IRC, HRC – sets the
output channel plan in use (uS broadcast, uS
standard cable tV, iRC, or HRC respectively)
· CHANNEL: 1-158 – sets the output channel number; the
range varies depending upon the channel plan selected
· PSIP: ORIGINAL, MODIFY, BASIC – the aCt1000 can
modify or insert PSiP tables as needed. oRiGiNaL passes
the incoming PSiP tables unchanged. moDify will modify
the incoming PSiP tables to user-defined channel numbers,
and BaSiC will insert newly-generated PSiP tables based on
user-defined settings; both of these settings must be used in
conjunction with the R. L. Drake Digital Headend Control
Program
1
, which allows the user to set the new values.
1 version 3.8 or later must be used – the newest version can be downloaded from http://giant.rldrake.com/RLDrake_Digital_Headend_Control.zip
