[time-nuts] 58503A alarm light on, but :SYSTEM:STATUS? indicates all is ok

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Sat Apr 4 11:49:20 EDT 2015


On 1 Apr 2015 23:24, "Bob Camp" <kb8tq at n1k.org> wrote:
>
> HI
>
> Best guess is that your antenna is not doing the job.

That's possible.  It was supposed to be an Andrews antenna,  but there's
nothing on it to indicate that to me. But it is well sited. I expect
antenna issues can explain the log entry

092:20150330.19:30:37:  Holdover started, not tracking GPS

> If the HP is in lock long enough to predict a good holdover (there are
multiple limits) you can have
> holdover with no alarm.

Which is what I did have with the above log entry.

Log 103:20150331.00:00:00:  Power on
Log 104:20150331.00:08:19:  GPS reference valid at 20150331.15:02:08
Log 105:20150331.15:03:16:  GPS lock started
Log 106:20150331.17:01:37:  Position hold mode started

> If it goes into holdover and is not “ok” by the various limits, you will
get an
> alarm + holdover.

But I have never seen that.

> After being in holdover for a while (how long depends) you will get an
alarm. Likely
> values are in the 24 hour range if it’s been on for a while.
But that never happened.

I got an email from someone else, who also has an 58503A, and says his
recently showed "Alarm", with nothing in the log. He postulated whether it
could be to do with the upcoming leap second, although I would have thought
that on such an old design, if such issues existed, they would have been
discovered before now.

I just checked the receiver a minute or two ago, and the Alarm LED was on,
as it has been for a few days now. I then sent

E-113> *CLS
scpi >  :SYSTEM:STATUS?

over the RS-232 and the LED went out. I want not expecting this, so can't
say whether the *CLS or the :SYSTEM:STATUS? caused it to go out. (I would
guess the first, but I don't know).

I note the display now shows the pending leapsecond, which it did *not*
when I posted this on April the 1st.

When would the clock be expected to know about the leapsecond? Somewhere
between the
8:59:42 on 1st April 2015 and 16:32:49 on the 4th April 2015, the receiver
seems to have learned about the leapsecond, which will be added at the end
of June.

See below, for what it shows now. The 9.2 us/initial 24 hrs is a lot worst
than it was a few days ago (4.9 us/initial 24 hrs), but 4.9 was unusually
low. I have never seen it that low before, but I don't keep watching this
thing all the time. I bought it mainly for a lab reference.

scpi >  :SYSTEM:STATUS?
------------------------------- Receiver Status
-------------------------------

SYNCHRONIZATION ............................................. [ Outputs
Valid ]
SmartClock Mode ___________________________   Reference Outputs
_______________
>> Locked to GPS                              TFOM     3
FFOM     0
   Recovery                                   1PPS TI -11.8 ns relative to
GPS
   Holdover                                   HOLD THR 1.000 us
   Power-up                                   Holdover Uncertainty
____________
                                              Predict  9.2 us/initial 24 hrs

ACQUISITION ................................................ [ GPS 1PPS
Valid ]
Tracking: 6 ____   Not Tracking: 1 ________   Time _____ +1 leap second
pending
PRN  El  Az   SS   PRN  El  Az                UTC      15:32:49     04 Apr
2015
 12  70 233   88    22  14 276                GPS 1PPS Synchronized to UTC
 14  29 310   39                              ANT DLY  0 ns
 15  20 171   39                              Position
________________________
 17  23  43   49                              MODE     Hold
 24  76 108   71
 25  30 239   33                              LAT      N  51:39:04.143
                                              LON      E   0:46:36.402
ELEV MASK 10 deg                              HGT               +47.15 m
(MSL)
HEALTH MONITOR ......................................................... [
OK ]
Self Test: OK    Int Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK
scpi >  :DIAG:LOG:READ:ALL?
Log status: 106 entries

<same as posted before - there are no new entries>

Dave



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