[time-nuts] Why is holdover LED on HP 58503A not lit, when GPS lock is unlit too?

[Artek Manuals]

I believe  the "Holdover" function only occurs when you you loose just 
the  satellites

Once locked disconnect the antenna for a minute and you will see the 
holdover LED light.

IF the unit looses POWER it has no way of of powering the oscillator and 
its ovens ( to do a holdover) and has no way of knowing how long the 
unit has been off when re-powered until it goes through a complete 
acquisition/re-sync cycle.

DAVE

manuals at artekmanuals.com


On 12/18/2016 8:01 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
> My 58503 GPS time/frequency reference had its power disconnected a few
> times yesterday as I moved things in the lab. At the modem the status of
> the LEDs are
>
> * Power green
> * GPS lock - not lit
> * Holdover - not lit
> * Alarm - not lit.
>
> That is what the manual says will happen  when power is first applied, but
> I'm puzzled why.
>
> The SYSTEM:STATUS? shows the information at the end of this email. What I
> can't understand is why the holdover light is not lit, when clearly its not
> tracking any satellites. It seems logical to me that holdover should be on,
> when GPS lock is not, and visa versa. But that does not seem to be the
> case.
>
> Looking at the data below, the date/time is obviously wrong (01 Jan 1998),
> the height at -14.04 m  (MSL) is wrong, but latitude and longitude look
> about right, although they are certainly not exactly agreeing with Google
> maps, which show 51°39'04.1"N+0°46'36.4"E.
>
> I must be misunderstanding the purpose of these lights.
>
> I'm also a bit puzzled it has been on about 1.5 hours, and can't seem to
> find a single satellite. The antenna is fairly clear of anything else, and
> it was certainly working yesterday, with the power and GPS lock LEDs both
> lit.
>
> Any ideas what's going on?
>
> 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: 1 ________   Time _____ +1 leap second
> pending
>                     PRN  El  Az                UTC      12:59:16 [?] 01 Jan
> 1998
>                     *32  -- ---                GPS 1PPS Invalid: not tracking
>                                                ANT DLY  0 ns
>                                                Position
> ________________________
>                                                MODE     Survey:      0%
> complete
>                                                         Suspended: track <4
> sats
>                                                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 >
>
>
>
> Dr. David Kirkby Ph.D CEng MIET
> Kirkby Microwave Ltd
> Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
> UK.
> Registered in England and Wales, company number 08914892.
> http://www.kirkbymicrowave.co.uk/
> Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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>

-- 
Dave
Manuals at ArtekManuals.com
www.ArtekManuals.com