Optional Ip67 Water-Proof Enclosure - Jackson Labs RSR GNSS Transcoder User Manual

RSR GNSS Transcoder™ User Manual
well as the overall simulation signal quality. The CSAC (as well as the TCXO on units without a
CSAC) can be automatically disciplined to an external 1PPS reference source which is typically a
user-supplied GNSS receiver, and the unit will go into holdover mode automatically when the
external GNSS receiver stops producing a 1PPS signal due to loss of GNSS lock etc. Both the 1PPS
output and the 10MHz output on connector J4 are generated by the internal TCXO locked to the
optional CSAC, and are thus highly-stable and accurate while exhibiting very low phase-noise. The
built-in CSAC is steered by the same algorithms used on the popular JLT CSAC GPSDO modules,
and provides a highly-stable atomic reference platform. As an interesting side-note: the
internally-generated 1PPS pulse and NMEA date/time information is also available to the USB port
DCD interrupt and serial port, and thus the unit can act as a standard PVT reference for NTP servers
under Linux using the industry-standard GPSD driver.
In the absence or failure of the CSAC on the module the internal TCXO is automatically controlled
by a built-in 24 bit DAC and optionally disciplined to an external 1PPS reference via JLT's GPSDO
disciplining algorithms. Switchover between the software-driven TCXO DAC and the analog PLL
locking the TCXO to the CSAC is automatic. The built-in CSAC oscillator can also be
powered-down manually through an SCPI command to reduce overal power consumption. The unit
will automatically revert to TCXO-only disciplining in the event the CSAC is powered-down, or fails
to operate properly for any reason.
Operation with the optional CSAC oscillator allows the unit to act as a time-transfer device to any
external GPS receiver. In stable conditions the CSAC can have drift rates of less than 2us per day,
thus allowing highly-accurate time-keeping when operating in GPS-denied environments, or when
generating IS-GPS-250A compatible Pseudolite signals for example. Accrued phase and frequency
errors inside the CSAC oscillator can be calibrated-out automatically and within a handful of minutes
by simply feeding-in an accurate and stable 1PPS reference source to the module.
For testing and evaluation the CSAC can be manually steered (CSAC:STEER xx command), and
steering values can be manually stored inside the CSAC NVRAM by issueing the
CSAC:STEER:LATCH ONCE command. Please see the CSAC GPSDO user manual for additional
details on the operation and monitoring capabilities of the built-in CSAC GPSDO sub-system.

3.7 Optional IP67 Water-Proof enclosure

The RSR GNSS Transcoder™ can be ordered with a ruggedized IP67 water-proof machined
anodized-aluminum enclosure. The unit can be operated inside the enclosure with or without the
optional CSAC oscillator. The internal USB connector pins and the pins of connector J4 are brought
out of the enclosure on a water-tight DB-15 female connector, and the RF SMA output connector is
available in the back of the enclosure. Four strong magnets on the bottom of the enclosure allow
mounting the unit on a vehicle roof or other metal surfaces, while four mounting holes allow a more
permanent mounting with screws or bolts. Rockwell Collins makes available a cable harness upon
demand to glue-lessly connect the Rockwell Collins RSR SAASM or M-Code puck receivers to the
RSR GNSS Transcoder™. Legacy GPS antennae can thus simply be replaced by the Rockwell RSR
Puck connected to the RSR GNSS Transcoder™, and an optional 5V (USB), or 7V to 36V (12V
nominal) power source connected to the cable harness. The RF output of the unit would simply be
connected to the legacy equipments' RF antenna input connector on top of the vehicle in this
scenario. A USB break-out cable can be used for software upgrades and configuration. The following
images show the optional RSR GNSS Transcoder™ IP-67 water-proof enclosed unit:
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