[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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