[ntp:questions] Re: questions on msf (via shm) clock

Jonathan Buzzard jonathan at uk.me.buzzard
Thu Dec 30 10:54:18 UTC 2004


On Mon, 27 Dec 2004 20:07:27 +0000, dave morgan wrote:

> Hi,
>   after a couple of false starts (transistor back to front,
> resistor connected to wrong pins :-/ ) I have got my MSF refclock
> working. This has raised the following questions -
> 
> a) will its jitter figure never go below 1?

>From my machine running the original hardware

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 LOCAL(1)        LOCAL(1)        10 l   43   64  377    0.000    0.000   0.004
*SHM(0)          .MSF.            0 l   36   64  355    0.000    0.183   0.497


> b) why does the refid for this clock show SHM(0), even though the 
> lines for it in the ntp.conf file is as follows?
> 
> #msf rx on serial port 1
> server 127.127.28.0 prefer
> fudge 127.127.28.0 stratum 2  time1 0.022  refid MSF

>From memory because you have changed fudged the stratum level.

> c) what stratum should I declare it? I have left it fudged to 2 for
> now as the jitter seems no better than the other stratum 2 servers
> I use.
> 

You should leave it at it's default stratum level of zero. This is because
what you have is a genuine stratum zero reference clock. All hardware
reference clocks that acquire their time from a remote source via radio or
microwaves are by definition stratum zero. Don't be fooled by the fact
that it did not cost very much.

JAB.

-- 
Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Northumberland, United Kingdom.       Tel: +44 1661-832195




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