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

[Dr. David Kirkby (Kirkby Microwave Ltd)]

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)