[ntp:questions] Question on loopstats and PPS

Mauro Fiacco Mauro.Fiacco at ipaccess.com
Thu Dec 15 09:12:48 UTC 2005


Pedro,

I know that the 6th field is the Allan deviation... However, it was
calculated only for 64seconds interval (time constant of 6). 

I am interested in the curve at much higher update intervals.

Any idea?

Regards,

Mauro

On Wed, Dec 14, 2005 at 02:58:14PM -0200, Pedro Torres wrote:
> Date: Wed, 14 Dec 2005 14:58:14 -0200
> From: Pedro Torres <torres at pop-pr.rnp.br>
> To: questions at lists.ntp.isc.org
> Subject: Re: [ntp:questions] Question on loopstats and PPS


> Hi Mauro,

> Em Qua 14 Dez 2005 12:27, Mauro Fiacco escreveu:
> > Hi to All,

> > I am tryng to evaluate how good is my NTP server. It runs freeBSD and
> > uses a rubidium PPS signal to discipline the frequency (no time
> > correction).

> > The following loopstats is typical:

> > 53667 64119.201 0.000000000 32.241623 0.000000954 0.003332 6
> > 53667 64184.203 0.000000000 32.233749 0.000000954 0.004881 6
> > 53667 64248.196 0.000000000 32.233749 0.000000954 0.004227 6
> > 53667 64311.199 0.000000000 32.233749 0.000000954 0.003661 6
> > 53667 64377.202 0.000000000 32.233749 0.000000954 0.003170 6
> > 53667 64443.205 0.000000000 32.223343 0.000000954 0.005883 6

> > The Time offset is 0, as it does not know any better; the stability is
> > reasonable... But why the frequency offset (4th field) is so high?

> > The status reported by ntptime, shows that the FLL and PPSSIGNAL are
> > active.

> > Shouldn't the frequency be corrected within the capability of the PPS
> > signal?

> > I understand that this value may be the frequency offset measured by
> > PPS.

> > In this case my question is: how can I calculate the Allan deviation of
> > my server without knowing the actual frequency offset?

> I think 6th field is Allan deviation.

> Pedro
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-- 
Mauro Fiacco 

ip.access Ltd                      
URL: www.ipaccess.com  




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