Why is holdover LED on HP 58503A not lit, when GPS lock is unlit too?
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)
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
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)
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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
On Sun, Dec 18, 2016 at 8:01 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkirkby@kirkbymicrowave.co.uk> 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)
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
On 18 December 2016 at 14:31, Tim Shoppa tshoppa@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
On 18 December 2016 at 17:34, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkirkby@kirkbymicrowave.co.uk> wrote:
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.
I mean it is NOW attempting to track 6 !!! Almost the opposite of what I
wrote.
I'm guessing it gave up attempting to track the satellite with a PRN of 32.
Dave
On 12/18/2016 9:34 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
*12 -- --- MODE Survey: 0%
complete
If it's still showing that after being on for five hours, maybe it needs
to be explicitly told to start a survey?
dr
On 18 December 2016 at 18:19, Dan Rae danrae@verizon.net wrote:
On 12/18/2016 9:34 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
*12 -- --- MODE Survey: 0%
complete
If it's still showing that after being on for five hours, maybe it needs
to be explicitly told to start a survey?
dr
I seem to be having some issues now with this. I've reset it, and entered
the approximate latitude, longitude, height, as well as date and time. The
commands below were executed, although NOT necessarily in the order give.
E-113> GPS:INIT:DATe 2016,12,18
E-113> gps:init:time 19,18,35
E-113> SYSTEM:PRESET
scpi > DIAG:LOG:READ:ALL?
Log status: 2 entries
Log 001:19970504.00:00:00: Log cleared
Log 002:19970504.00:00:00: System preset
The receiver seems to find satellites fairly quickly, tries to track them,
and is showing reasonable values for the things I set, like date, time,
position etc. However, the receiver doesn't seem able to track any
satellites, so not surprisingly the survey never starts. I assume it wont
start until it has tracked sufficient number of satellites.
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: 12 _______ Time
PRN El Az PRN El Az UTC 21:57:41 [?] 18 Dec
2016
6 20 67 12 76 56 GPS 1PPS Invalid: not tracking
* 7 -- --- 14 32 307 ANT DLY 0 ns
* 8 -- --- 24 42 129 Position
* 9 -- --- 25 58 259 MODE Survey: 0%
complete
*10 -- --- *31 10 299 Suspended: track <4
sats
*11 -- --- 32 45 274 INIT LAT N 51:39:03.825
INIT LON E 0:46:36.277
ELEV MASK 10 deg *attempting to track INIT HGT +29.99 m
(MSL)
HEALTH MONITOR ......................................................... [
OK ]
Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OK EFC: OK GPS Rcv:
OK
It will run overnight. Perhaps tomorrow it will sort itself out, but I'm
not too hopeful.
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)
It is looking much better now. I
- Powered off
- Left off for 30 s
- Pulled antenna out.
- Powered on
- Connected antenna, making sure if was firmly screwed in.
It then got GPS lock in a few minutes. It is running at reduced accuracy,
with the survey only 9.7% complete, but it is looking more hopeful.
I can't help feeling there should have been more informative status
available by the LEDs. The fact it is locked, but at reduced accuracy,
should really be visable from the front panel IMHO. Anyway, it seems to be
getting there - see below.
scpi > SYSTEM:STATUS?
------------------------------- Receiver Status
SYNCHRONIZATION ............................ [ Outputs Valid/Reduced
Accuracy ]
SmartClock Mode ___________________________ Reference Outputs
Locked to GPS: stabilizing frequency TFOM 3
FFOM 1
Recovery 1PPS TI -15.9 ns relative to
GPS
Holdover HOLD THR 1.000 us
Power-up Holdover Uncertainty
Predict 432.0 us/initial 24
hrs
ACQUISITION ................................................ [ GPS 1PPS
Valid ]
Tracking: 6 ____ Not Tracking: 3 ________ Time _____ +1 leap second
pending
PRN El Az SS PRN El Az UTC 22:39:23 18 Dec
2016
2 28 87 86 6 20 48 GPS 1PPS Synchronized to UTC
12 57 70 119 24 24 137 ANT DLY 0 ns
14 39 287 106 31 27 303 Position
25 76 284 96 MODE Survey: 9.7%
complete
29 37 194 79
32 39 249 109 AVG LAT N 51:39:04.205
AVG LON E 0:46:36.347
ELEV MASK 10 deg AVG HGT +42.42 m
(MSL)
HEALTH MONITOR ......................................................... [
OK ]
Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OK EFC: OK GPS Rcv:
OK
scpi >
On 18 December 2016 at 22:41, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkirkby@kirkbymicrowave.co.uk> wrote:
It is looking much better now. I
- Powered off
- Left off for 30 s
- Pulled antenna out.
- Powered on
- Connected antenna, making sure if was firmly screwed in.
It then got GPS lock in a few minutes. It is running at reduced accuracy,
with the survey only 9.7% complete, but it is looking more hopeful.
This does appear now to be working - see below. I'm not exactly sure what
was the secret to getting this to work, but the above procedure seemed ok.
scpi > SYSTEM:STATUS?
------------------------------- Receiver Status
SYNCHRONIZATION ............................................. [ Outputs
Valid ]
SmartClock Mode ___________________________ Reference Outputs
Locked to GPS TFOM 3
FFOM 0
Recovery 1PPS TI -8.3 ns relative to
GPS
Holdover HOLD THR 1.000 us
Power-up Holdover Uncertainty
Predict 9.6 us/initial 24 hrs
ACQUISITION ................................................ [ GPS 1PPS
Valid ]
Tracking: 6 ____ Not Tracking: 2 ________ Time _____ +1 leap second
pending
PRN El Az SS PRN El Az UTC 23:11:07 19 Dec
2016
2 31 69 83 6 15 34 GPS 1PPS Synchronized to UTC
12 41 80 110 32 27 234 ANT DLY 0 ns
14 37 266 81 Position
25 83 33 127 MODE Hold
29 55 195 135
31 42 301 75 LAT N 51:39:04.198
LON E 0:46:36.358
ELEV MASK 10 deg HGT +45.42 m
(MSL)
HEALTH MONITOR ......................................................... [
OK ]
Self Test: OK Int Pwr: OK Oven Pwr: OK OCXO: OK EFC: OK GPS Rcv:
OK
scpi >
David wrote:
This does appear now to be working - see below. I'm not exactly sure what
was the secret to getting this to work, but the above procedure seemed ok.
Time. It is not at all unusual for a 58503A that has no almanac (or an
out-of-date almanac) to take several days to achieve disciplined
operation (and much longer for the OCXO to fully stabilize). You may
get lucky and find that it happens faster, but don't count on it. FWIW,
HP GPSDOs often take longer than others to initialize.
Everyone, please remember -- GPSDOs can take significant time to
re-initialize. No need to post about what may be wrong until at least 3
days of continuous running after powering on. Chill.
Same with respect to crystal oscillators settling to low drift rates.
No need to worry about drift (retrace) for at least a month (sometimes 6
or even 12 or 24 months) of continuous running after powering on.
Honestly, the best thing to do is turn it on and forget about it for 3
days (GPSDO) or 1 month (crystal oscillator). DO NOT observe it (log
it, if you feel the need, and don't look at the log until after the 3/30
days).
Precise time and frequency require patience!
Best regards,
Charles