Spectracom VersaSync User Manual page 182

3.3 Managing References
Oscillator Phase Drift
The chart below provides typical stability performance for the oscillator types that can be found
in VersaSync units. These numbers are based on the oscillator being locked to a reference for
two weeks, but then loses GPS reception for an extended period of time, while the ambient tem-
perature remains stable.
This data can help you determine how long of a Holdover period can be tolerated, based on
how much time drift may occur after GPS input is lost. The larger the time error that can be tol-
erated by VersaSync clients, based on the oscillator installed, the larger the Holdover timeout
period can be set to.
Table 3-3:
1PPS Phase Drift in Holdover
- 4 hours
- 24 hours
- 7 days
To find out which type of oscillator is installed in your VersaSync, navigate to MANAGEMENT
> OTHER: Disciplining , and look for the line item Oscillator Type in the Status panel.
Typical Holdover lengths
The length of the allowed Holdover Timeout period is displayed and configured in seconds.
The table below provides example conversions for typically desired Holdover periods.
Table 3-4:
Desired Holdover Length Holdover Length (in seconds) to be entered
2 hours
24 hours
7 days
30 days
1 year
Configuring a Holdover value exceeding 30 days could result in a one-second time error in the
UTC or Local timescales until an external reference (GNSS or IRIG input) is restored or a
170
Estimated Phase Drifts
(no reference available)
Typical Holdover lengths in seconds
7200 seconds (default value)
86 400
604 800
2 419 200
29 030 400
Note: Due to Leap Seconds that are periodically inserted into the UTC and Local
timescales, it is not normally recommended to exceed 30 days of Holdover
without an external reference that can supply Leap Second information being
applied (such as GNSS).
OCXO
OCXO
(high performance)
3 µs 2.8 µs
40 µs 30 µs
1.2 ms 0.6 ms
CHAPTER •
3 VersaSync User Manual Rev. 6.0
CSAC
1µs
7 µs
100 µs