[time-nuts] TU30 jump second
kb8tq at n1k.org
Tue Apr 4 11:47:31 EDT 2017
> On Apr 4, 2017, at 10:01 AM, Bo Hansen <timenuts at rudius.net> wrote:
> Hi all
> The data can be a bit hard to read in an email. So I will give it another try.
> PC-time | Diff. | GPS-time | Diff.
> 011606.005 | 0.992 | 011604 |1
> 011607.013 | 1.008 | 011605 |1
> 011608.005 | 0.992 | 011607 |2 <--- The issue
> 011609.013 | 1.008 | 011608 |1
> 011610.004 | 0.991 | 011609 |1
> I used a terminal program to log the NMEA data to a file and do the PC timestamp. Calculations were done in a spreadsheet by me. The PC-time is kept under control by Meinberg and also OK vs. <http://www.time.is> during the time of observation.
> The PC-timestamp wobble is not the issue. It is a combination of the PC-time itself and the NMEA wobble. Nobody should expect the NMEA data to come at the same time every time relative to the 1 PPS. As Björn correctly points out it is always late and wobbles with processor load.
> Sometimes the 2-something lag can last for many hours - I have seen more than 48 h.
> The issue is the "seconds jump". The issue is not the relative difference between the PC-time and the GPS-time but the jump, e.g. using Tac32 reveals that the TU30 is always ~1200 ms late on in case of the "jump second" ~2300 ms late.
> I wonder if it has anything to do with the Week 1024 Syndrome?
We are roughly 2 years away from the next week 1023 to week 0 GPS rollover point. If you see this multiple times in a 20 year period
it is not a 1024 week issue ….
> Indeed the TU30 is a old device. I guess some 30 years if not more looking at the components. F/W I have no idea.
> The 10 kHz seems unaffected.
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
More information about the time-nuts