[time-nuts] PRS10 not locking to 1PPS

Fri Jan 8 16:03:29 UTC 2021

Hi,

The PRS 10 is now locking to the 1 PPS from the GPS.
I have checked by using an external Time interval analyser and phase
deviation between
Input and output PPS is stable. Also I can see that the magnetic MR setting
is steered.
So, the PRS10 is locking again to GPS and the MR is within the limits. Thats
works again.
However the internal TIC value is not send to the RS232 port.  
Also the frequency steering is not as fine as before.
The delay between 1PPS in and 1 PPS out has a phase difference drift between
3.68 and 0.60 uS as an 
trapezium and jumps about 600 seconds. 
The 3.6 us is the double of the 1840 ns wrong delay eeprom setting in the
PRS10.
Still some internal math error I think.
The external Time Interval Analyzer is a Yokogawa TA1100 which has a
resolution
of 1 ps/s. Single Shot. A older but nice instrument.

Regards,
Erik (PE1RQF)

-----Original Message-----
From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of Dana Whitlow
Sent: donderdag 7 januari 2021 18:11
To: Discussion of precise time and frequency measurement
<time-nuts at lists.febo.com>
Subject: Re: [time-nuts] PRS10 not locking to 1PPS

Erik,

When I was working at my last (pre-retirement) job, I encountered an old
PRS-10
gathering dust.  It worked well free-running, but when I tried to lock it to
1PPS, it would do nothing for a while, then would begin deviating further
and further from a correct lock.  Over a period of a few hours it would
basically run amok.

Dana

On Thu, Jan 7, 2021 at 10:10 AM <e.j.kroon at vathorstnet.nl> wrote:

> Hi All,
>
> I have done an experiment using the PSR10.
> I have set the Magnetic offset to mid-range MO2950 Than set the Set 
> frequency to 0 SF0. To have 0 frequency offset.
> Measured the output frequency and calculate the average deviation.
> By using the Frequency Synthesizer Table from Appendix A I have 
> selected the smallest frequency deviation by changing via the 
> Frequency Synthesizer Control command SP.
> Than measured the frequency deviation again and use the Set frequency 
> command for the correction of the deviation (by SF). By monitoring the 
> Magnetic read you are able to see the Magnetic C field effect from the 
> SF setting. Than enter the Magnetic offset to the value of magnetic 
> read via MO. Finally set the SF to 0.
> By this procedure the frequency deviation is < than a few parts to -12.
> And within the Magnetic offset range.
> However still the 1pps control is not working and stops the internal 
> time interval.
> Maybe by corrupted eprom TO setting.
> But the unit is good for un-steered operation.
>
> Thanks for your help
>
> Erik (PE1RQF)
>
>
>
> -----Original Message-----
> From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of Dana 
> Whitlow
> Sent: maandag 4 januari 2021 21:02
> To: Discussion of precise time and frequency measurement 
> <time-nuts at lists.febo.com>
> Subject: Re: [time-nuts] PRS10 not locking to 1PPS
>
> Erik, the PRS-10 does have provisions for changing the internal 
> synthesizer's "ratio",  which could provide a way of getting an 
> essentially fresh start on aging.
> There's a
> big table of values somewhere in the documentation (but not 
> necessarily in any convenient order).
>
> My old PRS-10 is getting towards one end of its magnetic tuning range 
> and will probably "die" in another couple of years use, but I have 
> high expectations of winning it back via this mechanism.
>
> Have you looked into this?
>
> Dana
>
>
> On Mon, Jan 4, 2021 at 1:36 PM <e.j.kroon at vathorstnet.nl> wrote:
>
> > Hi all,
> >
> > The PSR10 is working now for 15 years at my place (total >25 years).
> > For the 1pps a Trimble Resolution T is used and has a good 1pps signal.
> > The Magnetic Offset MO is on the limit value of 2300 when using the 
> > 1pps correction.
> > Therefore I think the unit is on end of life. I tried a factory 
> > reset to see what will happen.
> > However due to the change of the TO to 1814 the unit stopped 
> > measuring the 1pps time pulses after 256 measurements and no 1pps 
> > measurement are possible when PL=1.
> > The other values are responsive. Only after a RS1 it will measure 
> > again the pps.
> > My thought was due to the strange TO of 1814 (before factory reset 
> > is was
> > -1814)
> > the internal calculation is messed up.
> > When PL=0 the pps measurements continues but the MO is not 
> > controlled to GPS.
> > I am not sure how to update the firmware.
> > While the unit is still stable, it has now an frequency offset of
> > -2.7E-10 Hz/Hz stability still is
> > 2.4E-12 for 20k seconds.
> > Probably I need another rubidium frequency standard.
> >
> > ST5 when PL=0
> > 3 = PPL disabled,  < 256 good 1pps inputs Provide stable 1pps inputs
> >
> > ST5 when PL=1 and when 1pps hangs
> > 4 = Excessive time interval (while 1pps is still good of the GPS)
> >
> > Regards,
> > Erik (PE1RQF)
> >
> >
> >
> >
> > -----Original Message-----
> > From: Miikka Raninen <miikka.raninen at gmail.com>
> > Sent: zondag 3 januari 2021 21:44
> > To: time-nuts at lists.febo.com
> > Cc: e.j.kroon at vathorstnet.nl
> > Subject: PRS10 not locking to 1PPS
> >
> > > Hello Time-Nuts,
> > >
> > > I am an user of a PRS10 Rubidium standard.
> > > The unit has firmware revision 3.15.
> > > After reset to factory settings the Time Offset (TO) was set to 1814.
> > > Normally it was -1814. Now de PRS10 is not locking to the 1PPS
anymore.
> > > It will freeze when PL = 1. It will freeze after 256 seconds.
> > > Is there a known way to set the TO back to -1814 for the firmware
> > revision?
> > > As it is a factory setting for this firmware revision.
> > >
> > > Regards,
> > > Erik pe1RQF (former time keeper for the Netherlands at VSL)
> >
> > Ref manual for PRS10 :
> > https://www.thinksrs.com/downloads/pdfs/manuals/PRS10m.pdf
> >
> > Check the quality of the input 1PPS. When the unit fails to lock on 
> > to 1PSS input after 256 seconds it is usually due to the 1PPS being 
> > too unstable in phase
> >
> > What do you mean by freezing? Can you check the status bytes with ST?
> > command? They might indicate the reason for the fault :
> >
> > ST5: Frequency Lock to External 1pps
> > ST5 bit Condition which sets bit Corrective Action
> >
> > 0 PLL disabled Send PL 1 to enable
> > 1 < 256 good 1pps inputs Provide stable 1pps inputs
> > 2 PLL active
> > 3 > 256 bad 1pps inputs Provide stable 1pps inputs
> > 4 Excessive time interval Provide accurate 1pps
> > 5 PLL restarted Provide stable 1pps inputs
> > 6 f control saturated Wait, check 1pps inputs
> > 7 No 1pps input Provide 1pps input
> >
> > You might also want to consider updating the firmware as "(Note:
> > Firmware revisions prior to Rev 3.23 do not allow user TO! commands.
> > Check the firmware revision with the ID? command)"
> >
> > - Miikka Raninen OH3GPJ
> >
> >
> > --
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