Symmetricom Z3801A, User Manual

Page: 53 / 98

Chapter 3 Using the Receiver Status Screen
Using and Reading the Receiver Status Screen
User Guide 3-9
Figure 3-4. Receiver Status Screen Displaying Holdover Operation
In the SYNCHRONIZATION area, you can see that the Receiver has
gone into holdover as indicated by >> marker that is pointing at the
Holdover line. The status screen indicates that the reason the Receiver
is in holdover is because the GPS 1 PPS reference signal is invalid.
You would expect this since the antenna has been disconnected.
The status screen shows, instantaneously, loss of the GPS signal.
As you can see on the screen, all of the satellites in the Tracking
column moved into the Not Tracking column.
The status screen in Figure 3-4 shows that the Receiver has been in
holdover operation for 14 seconds.
If the Receiver SmartClock had had enough time to learn the internal
oscillator characteristics (24 hours), the Receiver status screen would
show that the Receiver went into holdover, and the Receiver’s outputs
were maintained during holdover by the SmartClock.
When the GPS antenna is re-connected and the GPS signal has been
re-acquired, the Receiver has the ability to recover from holdover by
itself. The SYNCHRONIZATION area of the screen will show the >>
marker pointing at the Recovery line (and then eventually at the
Locked to GPS line), the GPS Lock LED will illuminate, and the screen
will look similar to Figure 3-5.
SYNCHRONIZATION
Receiver Status
---------------------------- ----------------------------
[ Outputs Valid/Reduced Accuracy ] ...........................
.............................................
......................................................
ACQUISITION
ELEV MASK
Not Tracking: 7
Locked to GPS
UTC
ANT DLY
MODE
LAT
LON
HGT
HEALTH MONITOR
PRN
Recovery
Holdover: GPS 1PPS invalid
Power-up
SmartClock Mode
Satellite Status
Tracking: 0
Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OK EFC: OK GPS Rcv: OK
[ OK ]
Time
GPS 1PPS Inaccurate: not tracking
Position
Reference Outputs
El Az
*2 71 316
10 deg
3 2
1.000 us
[GPS 1PPS Invalid]
20:56:14 31 Jan 1996
0 ns
Survey: 71.1% complete
N
W
37:19:32.472
121:59:51.784
+42.19 m (MSL)
>>
*attempting to track
TFOM FFOM
HOLD THR
1PPS TI --
Predict 432.0 us/initial 24 hrs
Holdover Uncertainty
Holdover Duration: 0m 14s
Present 1.0 us
*7 41 186
15 11 86
*19 35 107
*22 68 78
*26 23 314
PRN El Az
*31 12 29