GNSS Receiver On
4. Turn the
GNSS Receiver = ON.
5. Set the
Satellite System = GPS
6. Set
In-survey time (s) = 600,
which is the time window used by the GNSS Receiver to assess stable location, using the specified
accuracy (below). Having an accurate tri-dimensional location is required to calculate accurate time.
7. Set
In-survey accuracy (m) = 5,
which is a target of <5m for the Mean V accuracy reading. Smaller values tighten the location
accuracy requirements, but the site survey process may take longer. It is possible to get better than 1.5m location accuracy when using
professionally-installed roof-top antennas.
8. Enter any antenna cable delay that needs to be compensated for (velocity of propagation is cable dependent, their values are around
5ns/m or 1.2ns/ft). Enter
20ns if
using the 5m portable antenna.
9. Select the
Time Zone Offset
(it is used to calculate the local time of day).
10. Wait for GPS Status on top to show Lock and the icon at the bottom of the screen turns green. It indicates that it is successfully
tracking enough GPS and GLONASS satellites.
11. Wait for about 15 to 30 minutes for the
Mean V
value to be below
5.00m
and until the
In Survey
status also shows
Locked
. This
indicates that the GPS position has reached the required accuracy (site survey finished) and that it has switched into Timing Mode.
12. At this point, the GPS Module should be providing accurate Time and Timing (1PPS).
13. Tap the
Sync ToD
button to synchronize the test set’s (system) real-time clock.
Atomic Clock Settings and Operation
This section explains the different disciplining parameters for the optional chip-scale Atomic Clock and provides the settings required to
quickly verify its proper operation. For application-oriented configurations, please refer to the suggested configurations table at the end of this
document.
Free Running Stage (Frequency only)
By default, the built-in Atomic Clock oscillator starts in free-running mode, providing a calibrated Atomic 10MHz frequency reference. (Its exact
frequency could vary over time due to ageing, temperature, storage and other factors.) It also produces an arbitrary (non-traceable) 1PPS
timing signal that is not aligned to the standard UTC second. Disciplining must be used in order to make the necessary frequency and timing
corrections.
Oscillator Disciplining Process (Frequency & Phase)
The disciplining process acts as a continuous “soft calibration” that corrects any frequency deviation in the oscillator and aligns the timing
pulse (1PPS) to the standard UTC second. The chip-scale atomic oscillator can be disciplined by:
1. The built-in precision GNSS Receiver (GNSS 1PPS).
2. An external traceable 1PPS signal from a primary reference time clock (PRTC) or time standard (Cs or Rb).
Clock Disciplining - Using the built-in GNSS 1PPS
1. With the GNSS module already locked, go to
>Utilities >Settings >More >High Precision Clock >Atomic Clock.
2. Set
Discipline Source = GNSS 1PPS,
to use the traceable (UTC aligned) 1PPS timing signal from the GNSS receiver.
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