Re: NTP clock source

[todd glassey <tglassey () earthlink net>]

On 3/25/2010 7:03 AM, Dave Hart wrote:
> On Thu, Mar 25, 2010 at 12:51 UTC, Kyle Bader <kyle.bader () gmail com> wrote:
> > Can anyone recommend a solid clock souce (stratum 0) that's not overly
> > expensive?
>
> All the options I'm aware of have no prices posted, sadly.  For me,
> that means "forget it, you don't want to spend that much", but then
> I'm not spending other people's money :)
>
> In addition to Symmetricom and EndRun Technologies, Meinberg has a
> solid reputation in this space:
>
> http://www.meinberg.de/english/products/#network_sync
>
> I'm biased toward Meinberg because several of their staff contribute
> their skills to the development and maintenance of the ntp.org
> reference implementation.  They have also been generous donating
> hardware over the years to ntp.org and pool.ntp.org, and their Windows
> NTP binaries and GUI installer are widely used.

I totally agree! Meinberg's M300's rock solid and JTime is really easy
to deal with as are its distributor's.

> The cheapest solution involves the Garmin GPS 18x LVC receiver and a
> soldering iron.  Unlike the USB and "PC" (232) versions of the GPS
> 18x, the LVC version supplies a pulse-per-second signal which makes it
> suitable for sub-millisecond NTP sync.  The supplied connector has to
> be cut off, a DB-9 serial hood wired in its place, and either a USB
> cable or other 5V power supply needs to be attached.  Or you can do as
> I did and pay for the completed GPS 18x LVC with DB-9 and USB
> connectors from a third party.  $105 from:

True - you can build very accurate timekeeping service practices, but
ALL GPS-L1 based systems have one flaw - the provability of the time
data is squat. The evidence-model from a passive L1 system no matter how
accurate it is - is zero... zip... it has as much legal impact with a
competent lawyer on the other side, as you looking at mickey on your
wrist and setting the ToD by hand daily.

This  is becoming more and more important in the world of commercial
computing and something that timekeeping will have to morph towards to
insure its not unseated...

> You also need a junkbox PC with real serial ports (not via a USB
> adapter), or the capacity on an existing server.  The GPS 18x cable is
> either 3m or 5m long, if your PC is not close enough to a
> southern-exposed window or to roof access for the 18x to lock, you may
> also need a RS-232 extension cable and USB power supply.  Unlike
> timing-focused GPSes, the 18x needs 3 or more birds in view to provide
> a PPS signal.
>
> Good luck,
> Dave Hart

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