[ntp:questions] Meinberg NTP monitor, silly question

G8KBV g8kbv at nospam-uko2.co.uk
Sun Dec 20 11:23:17 UTC 2009

In article <ae645d02-818d-474c-9e44-e793b37e65c7
@h40g2000prf.googlegroups.com>, davehart at gmail.com says...
> On Dec 20, 00:32 UTC, G8KBV wrote:
> > But what does 'o' mean?
> It means the PPS peer, and when present effective trumps any * seen.
> > The "Application Log" shows:-
> > Using user-mode PPS timestamp for GPS_NMEA(2)  Not that I think it'll
> > make any significant difference, but I thought I'd set all this up so
> > that the PPS thing would run in Kernel mode, but obviously not.
> So (NMEA) is using the user-mode hack to get DCD
> timestamps, which is only effective when you restrict the GPS to one
> sentence per second.  However, (atom/PPS) is using real
> kernel-mode PPSAPI timestamps.  In this configuration, NMEA is
> "numbering the seconds" with its sloppier timestamps, and once its
> offset is under .4s, the PPS refclock takes over with its interrupt-
> time timestamps.
> > State   Remote          Refid           Stratum Type            When    Poll
> >         Reach   Delay   Offset  Jitter
> > *    GPS             0       Local clock     9       16      377
> >         0.000   0.089   0.006  
> > o       PPS(2)          PPS             0       Local clock     8       16      377
> >         0.000   0.124   0.004
> The jitter figures are nice and low for Windows.  I would hope the
> offset to PPS(2) would eventually be trimmed to 25us or less, and even
> with temperature swings you might hope to keep within 150-200us at
> worst.
> Cheers,
> Dave Hart

Thanks Dave.

AFIK I have all the right things pointing in the right places, but...

The PPS jitter this morning is still some 0.004mS, but the offset is 
down to 0.077mS   From what you say, not too shabby.

The system running it does seem temperature sensitive, not helped by 
being in an unheated room, often with a window cracked open to get the 
heat out!  My problem here is keeping the room cool most times!

The same PC is also running the GB3RAL 5Mhz beacon monitor program, as 
it's one machine that has a working soundcard that is not used for 
anything else.  It's a P4 1GHz machine, with 512Meg of RAM, running 
Win2k SP4 + all updates.

I have not (yet) ticked the box to optimise the system for background 
events.  I want to let this "settle" for a few days, then I'll try that 
and see what the difference (if any) is.

My need is for something *MUCH* better than the servers I can get to via 
the somewhat variable (latency) ADSL connection I have.  So far, though 
probably not to "Time Nuts" standards, it is a *HUGE* improvement over 
what I had.

Seasons Greatings etc and so forth.

Dave Baxter.

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