Message-ID: <8840D182F8BB7540B173D2B1FA0CA9AB018AE32F@argos.clb.tcfr.thales>
From: Jean-Louis.RAULT@fr.thalesgroup.com
To: rsgb_lf_group@blacksheep.org
Date: Fri, 13 Feb 2004 09:59:38 +0100
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Subject: RE: LF: Timing GPS
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Hi all

Please keep in mind that Windows operating systems are very poor "time
keepers".
They drift very quickly, depending on the programs you are running.
A drift of one second up to one minute per day is not uncommon (specially
with "data crunchers" softwares like real time FFT computing)!
I'm not talking about the drift of the PC hardware clock itself which is
quite good (the time base xtal oscillator drifts around 2 s per month on my
own computer), but from the Windows time management.
It seems that the time management on the Windows multitask OS has a very low
priority ...
I verified this on Windows 95, Windows 98 and Windows Me.
Any other experience with other operating systems ?

73 de Jean-Louis F6AGR


> -----Message d'origine-----
> De : 0482183881-0001@t-online.de [mailto:0482183881-0001@t-online.de]
> Envoyé : jeudi 12 février 2004 23:19
> À : rsgb_lf_group@blacksheep.org
> Objet : Re: LF: Timing GPS
> 
> 
> Stewart Bryant schrieb:
> > If GPS is not an option, then NTP (clock timing via the Internet)
> > might be an alternative.
> >
> > There is some info on accuracy at
> >
> > http://www.ntp.org/ntpfaq/NTP-s-algo.htm#AEN2361
> >
> > - Stewart G3YSX
> >
> Hi Stewart es All,
> I do some PC clock synchronizations via internet using the program
> "Time Watch", downloaded from http://www.blue-series.de. the 
> NTP server
> transmitting the synchronization signals must be in your vicinity.
> it is not usefull telling us that their timer is <1uS accurate 
> (in my case dirived from GPS receivings) if there is a long 
> wire to the
> server. it`s something else if you would know the phase fault 
> on the line 
> and can correct it in some way.
> 
> reading the PC clock in mSec from the window "Time Decoder" of SpecLab
> of one PC with the clock (motherboard and sound card) permanent 
> synchronized by the standard time signal station DCF77 and at the 
> same time reading the mSec from the screen of the other PC just 
> clocking by the signals from the internet server, I believe I see
> a difference, DCF77 in front.
> 
> be that as it may, we should reach an agreement about what kind of 
> synchronization we will make use of.
> 
> there is a problem in synchronizing the PC clock by DCF77 (as 
> with other 
> standard time signal transmitters): During lf transmittings 
> of your own 
> station there will be no clocking because the DCF77 receiver will be 
> overloaded (what is it in english "zugestopft"?).
> 
> if the program "Africam" will come into fashion agn (I played with it 
> and the SD KIT abt 20 years ago) the case is`nt as critical 
> as it sounds:
> if I rember right there are two helpfull knobs, Autotrack and 
> Aütofrequency.
> 
> BTW. if my station transmits all night long my neighbour runs 
> into trouble with his employer: the radio alarm synchronized by DCF77 
> doesnt wake him (the neighbour) up.
> 
> regards
> Uwe/dj8wx
>  
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> 
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