Strata Operations Guide
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Therefore, where both a TCU and TXU are used, total system control may be accomplished using front
panel or remote control from either housing.
MPEG/COFDM Encoder/Modulator
This is the heart of the Strata TX digital mode circuitry. This versatile circuit may be configured to
accept a wide range of digital or analog video and audio signal inputs and provide COFDM (70 MHz), IF
(70 MHz) or ASI video signal outputs. When installed in a TCU housing, the various signal inputs and
outputs are connected through the TCU Combiner circuit where the various signal inputs and outputs are
switched using software controls.
FMT
The optional FMT module accepts standard NTSC or PAL analog video and audio signals and FM
modulates these signals on a 70 MHz carrier. Using the MRC supplied configuration software, four
different audio sub-carrier frequencies may be defined in which up to four standard audio signals may be
transported with the associated video signal. Note that audio deviation levels are software controlled and
must be provisioned at the MRC factory when ordering this option.
TCU
The TCU may house either or both digital and analog video modulation modules. Where a customer
application might initially employ only analog video transmission but anticipates migrating to dual
(switchable) analog and digital operation, the TCU may be upgraded to add the MPEG/COFDM module
to provide this additional capability. Where only digital or analog video transmission is desired, the
MPEG/COFDM or FMT modules may be installed in a TXU housing thereby eliminating the need for a
TCU. Note that the Strata TX design does not permit splitting digital and analog video modulator
modules between a TCU and TXU. A TCU configuration may also include a “stand-alone” option where
either or both MPEG/COFDM and FMT modules may be used independent of the TXU. This
arrangement permits using a TCU equipped with analog and/or digital video modulation modules for a
variety of signal input and signal output configurations, including a digital option using NTSC or PAL
composite video input and ASI (digital) signal output.
TXU
The TXU always houses the IF/RF module, which accepts either a 70 MHz COFDM, FMT IF, or external
70 MHz input signal and up-converts these signals to the appropriate RF band. The RF frequency
synthesizer circuit included in the IF/RF unit, along with the command and control module, provide the
means to channelize RF video and audio signals in the 2 GHz RF band. Standard U.S. FCC band plans,
as well as customer created channel plans, may be accommodated using the Strata TX Windows based
configuration software. As noted above, the TXU may also include either an MPEG/COFDM or FMT
module (but not both) in which case the TXU serves as a stand-alone digital or analog video microwave
transmission system.
HPU
The optional HPU (High Power Unit) is designed to work with a companion TXU in which case RF
output signals from the TXU are connected to the RF input jack of the HPU. In the case of analog
microwave transmission, the RF output of the TXU is amplified operating the HPU RF amplifier in the
non-linear region (saturated) providing RF output levels at the 12 watt level (+41 dBm). In the case
where COFDM RF signals are used, software controlled back-off attenuation is applied to operate the
HPU RF amplifier in the linear region.
