[time-nuts] More GPS testing, KS-24361 quirk
Hal Murray
hmurray at megapathdsl.net
Thu Aug 27 05:41:34 EDT 2015
More testing...
I lost everything from roughly 12:00-24:00 UTC Tue and 10:00-20:00 UTC Wed
I stumbled into an interesting quirk in the KS-24361.
Short version:
After it has been in holdover for 5 or 6 minutes, the GPS unit switches to
tracking the non-GPS unit and says it isn't in holdover mode anymore.
Long story:
I have a program collecting statistics. It was plugged into the unit with
the GPS, aka Secondary. A graph of holdover time didn't make sense.
The response to ":ROSC:HOLD:DUR?" is something like 3.08000E+002,1 I think
the 1 at the end says it's in holdover mode and the 308 is the number of
seconds it has been in holdover. Graphing holdover shows the ramp I expect
for 5 or 6 minutes. Then it drops out of holdover. It returns to holdover
for a minute or two when I expect it to be recovering.
Digging deeper, the status page switches from
>> Holdover: GPS 1PPS invalid
to:
>> Recovery: fine freq adj [TI -50.0 ns] 1PPS TI -50.0 ns relative to Ext
and then to
>> Locked to Ext: stabilizing frequency TFOM 3 FFOM
1
The other box, non-GPS, aka Primary, does stay in Holdover.
--------
-------------------------- Secondary Receiver Status
--------------------------
SYNCHRONIZATION ............................................. [ Outputs Valid
]
SmartClock Mode ___________________________ Reference Outputs
_______________
>> Locked to Ext TFOM 3 FFOM
0
Recovery 1PPS TI +50.0 ns relative to Ext
Holdover HOLD THR 1.000 us
Power-up Holdover Uncertainty
____________
Predict 11.5 us/initial 24 hrs
ACQUISITION ................................................ [ Ext 1PPS Valid
]
Tracking: 0 ____ Not Tracking: 10 _______ Time
____________________________
PRN El Az PRN El Az UTC 06:40:32 27 Aug
2015
* 1 55 270 *31 64 90 GPS 1PPS Invalid: not tracking
* 3 35 310 *32 72 352 ANT DLY 1.000 us
* 4 52 216 Position
________________________
*11 37 243 MODE Hold
*14 23 56
22 17 114 LAT N 37:26:04.813
*23 23 260 LON W 122:12:15.762
25 10 55 HGT +9.95 m
(GPS)
ELEV MASK 10 deg *attempting to track
HEALTH MONITOR ......................................................... [ OK
]
Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OK EFC: OK GPS Rcv:
OK
--
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