Chapter 3
High Accuracy Timing
Configuring the module
T-BERD/MTS/SC Timing Expansion Module User Manual
July 2017
22112315, Rev. 004
Page 31
2
In
GNSS System
, select the value representing the GNSS system (or systems)
supported in the region where you intend to conduct testing. If you want to use
Satellite Based Augmentation Systems (SBAS) to augment the GNSS system (or
systems), select the option that provides SBAS (indicated with
+ SBAS
).
3
Specify the remaining values as follows:
a
Select the
Time Type
(GPS or UTC), then select the
Time Format
(12-hour
or 24-hour).
b
In
Elevation Limit (deg)
, specify the elevation limit in degrees. This value
represents
the lowest point on the horizon
on which the receiver will try to
locate and obtain information from GNSS satellites. The default elevation is
set to 5 degrees.
Using satellites near the horizon may degrade performance.
c
In
Minimum C/No (dB-Hz)
, specify the minimum Carrier to Noise Ratio (C/
No) for the satellite signals that will be used by the module’s GNSS receiver.
The C/No is an indication of signal strength ranging from 0 to 50 dB-Hz. The
default value is 9 dB-Hz.
Using satellites with a weak C/No may degrade
performance.
d
Select the
Antenna Power
(0, 3.3, or 5 volts). If you select 3.3 or 5 volts, the
TEM Module will report a fault if the antenna is not drawing sufficient current
(and therefore appears to be either disconnected, damaged, or defective). If
you are using a passive antenna or splitter (another device is providing power
to the antenna), or you are using a special low-power antenna, select 0.
e
The default
Antenna Time Bias
value is 28 (the optimal value for the Viavi
qualified antenna). If you are using a different antenna, determine the optimal
bias value by referring to the vendor specifications for the antenna (and, if
applicable, splitter or amplifier), then specify the bias value in nanoseconds.
This value represents the bias that is used to compensate for the delay intro-
duced by your antenna, the antenna’s cable, and if applicable, an in-line
splitter or amplifier where absolute accuracy of PPS is important. You can
also specify a bias value if you need to adjust the absolute timing of the TEM
Module to match other instruments or standards.
The GNSS settings are specified; proceed to
“Specifying location settings” on page 31
.
Specifying location settings
If you are using GNSS timing as your synchronization source, you must specify settings
that indicate that the TEM Module should survey satellite constellations and generate
accurate coordinates, or that your instrument will remain in a fixed position and you will
provide the latitude, longitude, and altitude of the instrument.
Survey settings
If you intend to use the module to survey GNSS constellations to generate accurate
coordinates, you must select a survey mode. If you select the Manual survey mode, you
must also specify the survey position accuracy and the duration of the survey.
