Jackson Labs RSR GNSS Transcoder, User Manual

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© 2017 Jackson Labs Technologies, Inc. 35
RSR GNSS Transcoder™ User Manual
command sets the currently accumulated UTC to GPS offset in seconds before any pending leap
seconds. The SIM:TIME:LEAP:DATE command sets the date of a current or previously pending
leap second. And the SIM:TIME:LEAP:DURation command sets the duration of the next pending
leap second.
As an example, to simulate the the December 31, 2016 leap second event with the simulation
beginning 30 minutes before the event, enter the following commands:
SIM:MODE MANUAL
SIM:TIME:START:TIME 23,30,00
SIM:TIME:START:DATE 2016,12,31
SIM:TIME:LEAP:ACC 17
SIM:TIME:LEAP:DATE 2016,12,31
SIM:TIME:LEAP:DUR 61
SIM:COMMAND START
The simulation should be started with sufficient time for the target receiver to download the UTC
correction parameters which can take up to 12.5 minutes.
3.8.13 Simulating 1023 Week Number Rollover
Using the start time- and date parameters described in Section 3.8.11 , the start time can be selected
to simulate a week number rollover event that some GPS receivers have difficulty handling properly.
For example, to simulate the upcoming April 6, 2019 week number rollover event, enter the
following commands:
SIM:MODE MANUAL
SIM:TIME:START:TIME 23,30,00
SIM:TIME:START:DATE 2019,4,6
SIM:COMMAND START
The simulation will start 30 minutes before the event and continue indefininately. You can end the
simulation with the SIM:COMMAND STOP command.
3.8.14 Simulating for GPS Spoofing
The RSR GNSS Transcoder™ can generate an GPS L1 output that is synchronized to live-sky GPS
signals. These live-sky and simulated signals can be combined together with a low-cost passive RF
combiner/splitter so that a target receiver will start tracking the simulated signals instead of the live
signals depending on relative power levels between the two signal sources. Using both user-uploaded
ephemeris and ionospheric correction data as well as time sychronized from an external GPS
receiver, it is possible to mix the RSR GNSS Transcoder’s RF output with a live-sky GPS signal for
spoofing simulations of live GPS signals. The external GPS receiver should be connected with
NMEA and 1PPS input to the RSR GNSS Transcoder™. Care must be taken to avoid re-broadcasting
simulated RF signals through the live sky antenna, and this is usually accomplished by using passive
RF combiners and GPS antennae with good rejection and isolation.
The following commands will configure the simulation mode, simulation time and the fixed
(spoofed) position: