[ntp:questions] Standalone PC Clock Sync

Richard B. Gilbert rgilbert88 at comcast.net
Sun Nov 4 18:17:56 UTC 2007

Russell, David wrote:
> I have a PC running Windows that gets disconnected from the network for
> up to an hour.  I am using NTP to sync the clock while it is connected
> but when disconnected the clock drifts quite a bit.  Does anyone have
> any suggestions for how I can maintain the timing in this scenario?   
> Also, I have been looking for a PCI card that would give me better clock
> accuracy than the standard Windows clock.  Sub-millisecond accuracy
> using NTP is the objective.
> Thanks,
> David Russell

You can purchase a PCI card from either Meinberg Funkurhren or 
Symmetricomm.  Expect to pay $1100 US and up, especially up!  These are 
equipped with a precision crystal oscillator, optionally an Oven 
Controlled Crystal Oscillator (OCXO).  They can be equipped with an 
optional GPS receiver.  The Symmetricomm products are the BC635PCI
and the BC637PCI (with built in GPS).  I don't recall what Meinberg 
calls their product.

With GPS input, these products can give you sub-microsecond accuracy. 
Even without the GPS input they can keep time as accurately as you can 
set the clock.  They are overkill for most people.

An inexpensive GPS receiver such as the Garmin GPS18LVC ca. $100 US can 
do much the same for you if you can site an antenna with an unobstructed 
view of the sky.  The principal difference is the "holdover" capability 
of Symmetricom and Meinberg products; though they are not, in 
themselves, primary standards they are extremely good clocks and will 
exhibit extremely low drift.

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