Viavi T-BERD 5800, User Manual

Page: 79 / 100

Chapter 6 Troubleshooting
Performing tests
T-BERD/MTS 5800 Timing Expansion Module User Manual
July 2017 22112315, Rev. 004 Page 63
No GNSS Time is detected
There are several reasons why GNSS time may not be detected:
• Verify that the GNSS antenna is properly connected (see “Connecting a GNSS
antenna” on page 10 ), and that the antenna power level specified is correct for the
antenna that you are using (see “Specifying GNSS settings” on page 30 ).
• Verify that you have specified a GNSS system as the synchronization source with
supporting settings (see
“Specifying GNSS settings” on page 30 ).
• Observe the Sky Plot to determine whether satellites within a constellation for the
GNSS system(s) that you specified are in view (see
“Sky Plot” on page 53 of
Chapter 5 “Timing and 1 PPS Analysis Results” ).
• Determine whether any of the satellites are used (indicated in green on the Sky
Plot, and as a test result in the GPS Status category). For details, see
“Sky Plot”
on page 53 , and “Status” on page 56 of Chapter 5 “Timing and 1 PPS Analysis
Results”
No GNSS Satellites are located
There are several reasons why GNSS satellites may not be located (or the module only
locates a small number of satellites):
• Verify that the GNSS antenna is properly connected (see “Connecting a GNSS
antenna” on page 10 ), and that the antenna power level specified is correct for the
antenna that you are using (see “Specifying GNSS settings” on page 30 ).
• Verify that you have specified a GNSS system that is available worldwide (for
example, GPS or GLONASS), in your geographical region (for example, BeiDou),
or both (for example, GPS
and BeiDou). For details, see “Specifying GNSS
settings” on page 30 .
• If the module only located a few satellites, you can optimize the number of satel-
lites located by selecting multiple GNSS systems as the synchronization source
(for example, you can use GPS and GLONASS concurrently). For details, see
“Specifying GNSS settings” on page 30 .
• Verify that you specified the Elevation Limit (deg) value, which represents the
lowest point on the horizon on which the receiver will try to locate and obtain infor-
mation from GNSS satellites. If the value is too low, there may be obstructions
preventing the antenna from receiving signals with almanac data. For details, see
“Specifying GNSS settings” on page 30 .
• If you are using the TEM Module inside a building (for example, in a lab environ-
ment), verify that the building is equipped to receive GNSS signals.
Performing tests
The following section addresses questions that may be asked about completing tests
with the connected TEM Module.