[time-nuts] Why is holdover LED on HP 58503A not lit, when GPS lock is unlit too?
Dr. David Kirkby (Kirkby Microwave Ltd)
drkirkby at kirkbymicrowave.co.uk
Sun Dec 18 17:34:55 UTC 2016
On 18 December 2016 at 14:31, Tim Shoppa <tshoppa at gmail.com> wrote:
> A common misconception, is that holdover is the opposite of GPS lock.
> Sometimes we might even talk about the two as if we're in one or the other.
> But really the power-on state, is that we're in neither holdover or GPS
> lock.
>
> Holdover means the smartclock previously had GPS lock and had used it to
> characterize the aging of the OCXO, and is maintaining the EFC
> extrapolation, such that it believes it can still produce accurate time and
> frequency through the GPS loss.
>
> The state of your clock at the moment, is that it has never had GPS lock
> since regaining power, it does not know what time it is, and it has not
> characterized or extrapolated the aging of the OCXO. So it is definitely
> not in holdover.
>
> Tim N3QE
>
Cheers Tim, that makes sense.
I'm a bit concerned it has not managed to track a single satellite, despite
it has been on 5 hours or so. But perhaps things have improved, as its not
attempting to track 6 (PRN=15, 2, 21, 25, 26 and 28), whereas before it was
attempting to track just with a PRN of 32. I'm hoping its current status
(see below), is looking more hopeful than what it was before.
scpi >
scpi > SYSTEM:STATUS?
------------------------------- Receiver Status
-------------------------------
SYNCHRONIZATION ........................................... [ Outputs
Invalid ]
SmartClock Mode ___________________________ Reference Outputs
_______________
Locked TFOM 9
FFOM 3
Recovery 1PPS TI --
Holdover HOLD THR 1.000 us
>> Power-up: GPS acquisition Holdover Uncertainty
____________
Predict --
ACQUISITION .............................................. [ GPS 1PPS
Invalid ]
Tracking: 0 ____ Not Tracking: 6 ________ Time _____ +1 leap second
pending
PRN El Az UTC 14:43:22 [?] 01 Jan
1998
*15 -- --- GPS 1PPS Invalid: not tracking
*20 -- --- ANT DLY 0 ns
*21 -- --- Position
________________________
*25 -- --- MODE Survey: 0%
complete
*26 -- --- Suspended: track <4
sats
*28 -- --- INIT LAT N 51:39:03.825
INIT LON E 0:46:36.278
ELEV MASK 10 deg *attempting to track INIT HGT -14.04 m
(MSL)
HEALTH MONITOR ......................................................... [
OK ]
Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OK EFC: OK GPS Rcv:
OK
scpi > SYSTEM:STATUS?
------------------------------- Receiver Status
-------------------------------
SYNCHRONIZATION ........................................... [ Outputs
Invalid ]
SmartClock Mode ___________________________ Reference Outputs
_______________
Locked TFOM 9
FFOM 3
Recovery 1PPS TI --
Holdover HOLD THR 1.000 us
>> Power-up: GPS acquisition Holdover Uncertainty
____________
Predict --
ACQUISITION .............................................. [ GPS 1PPS
Invalid ]
Tracking: 0 ____ Not Tracking: 6 ________ Time _____ +1 leap second
pending
PRN El Az UTC 16:59:08 [?] 01 Jan
1998
* 8 -- --- GPS 1PPS Invalid: not tracking
*10 -- --- ANT DLY 0 ns
*11 -- --- Position
________________________
*12 -- --- MODE Survey: 0%
complete
*13 -- --- Suspended: track <4
sats
*30 -- --- INIT LAT N 51:39:03.825
INIT LON E 0:46:36.278
ELEV MASK 10 deg *attempting to track INIT HGT -14.04 m
(MSL)
HEALTH MONITOR ......................................................... [
OK ]
Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OK EFC: OK GPS Rcv:
OK
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