[time-nuts] New to Time Synching hardware - needing some advice
gsricalde at gmail.com
Thu Dec 27 18:48:28 UTC 2012
It could be possible to use two Rb GPSDOs, one providing the PPS and
another disciplined by GPS, then rotate them every month.
On Fri, Dec 28, 2012 at 2:41 AM, Attila Kinali <attila at kinali.ch> wrote:
> On Thu, 27 Dec 2012 10:19:46 -0800
> Chris Albertson <albertson.chris at gmail.com> wrote:
>> Yes you could us something like one of the low-cost rubidium
>> oscilators to supply a pulse per second to Linux NTP and it would work
>> for some time before the error was as large as 10 mS.
>> One missing requirement is how long you need be without GPS or
>> networking. Obviously you can't stay out of contact with the world
>> forever but it is very easy and cheap if you only need a day. Harder
>> if you need a month and expensive if you are talking about years.
> Actually, a couple of months is still quite simple.
> The Rb approace gives you at least something in the range of 10^-9 stability,
> long term. Which gets you into the ballpark of 100 days (with 10ms). If you
> temperature stabilize the Rb you should get down to 10^-11, which would
> be 30 years. At least theoretically, aging is AFAIK larger than this.
> But a couple of years should be still possible without too much effort.
> IIRC the FE5680 sell now for 200USD. Some heatsink and temperature control
> come maybe at 50-100USD. Some equipment to measure where the PPS lies
> relative to UTC and a powersupply that can get you 15V from mains and
> a battery (to get the Rb where the computer is) would also be necessary.
> Alternatively, put the Rb next to the computer in question, hook a powerfull
> linedriver to the PPS output, and a wire that goes all the way out where
> you have GPS reception and can measure the PPS pulse. After measurement,
> you can remove that cable.
> Ofcourse this only works, if you can lay a cable temporarily. If you are in a
> EMP secured room, the only way to get the pulse measured is the approach
> with the traveling Rb.
> Attila Kinali
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