Hi Rather than getting uber crazy, how about something simple:
Take a cheap telecom Rb from the usual auction sites. Get it running and on frequency. Probably hook a battery into the power supply for backup. Run it's pps into the PC. At this point you should (with some luck temperature wise) be at < 5x10^-11. It should stay at this level for quite a while. You should be good to a second for many years. The only thing you need to do now is a "clock trip" with your wrist watch to set the system each time the PC looses power. I'm guessing that the bunker has pretty good backup power. If not, code up a little PIC to keep time when on battery power. If you go the battery / PIC route, you probably could set it outside the room and get it a bit closer than you can with your wrist watch. If you want to go to the next level with this, do a time check in a couple of years. Correct the Rb for the average error. That should get things *very* close long term. That of course assumes your bunker has better temperature control than mine does …. Bob On May 17, 2013, at 12:45 AM, Grant Waldram <gr...@remobs.com.au> wrote: > Hi folks. I wouldn't call myself a time nut, so this is really an effort to > ask for advice from some people who know the field. My first contact with > time synchronisation was looking at the instrumentation clocks for the > Woomera rocket test facility when I went out there for a few (large!) hobby > rocket launches. I can't even remember the system's name but it used a > series of pulses of various lengths to give a unique time code. But, I > digress... > > > > I've not had much need for time synchronisation over the years, but in > recent years NTP has been able to get me by. Unfortunately I'm now faced > with a network that needs a moderately correct clock (I'm scared of using > the word 'acurate' around you folks!) to the order of a few seconds or so, > but with no possibility of an external internet connection (for a number of > reasons). At present I'm using one PC running Windows Server as an SNTP > server to synchronise all of the devices, as it is the only device in a > physically secure location. This is inside a security-fob protected room. I > can't get GPS signals in there, and the Australian radio clock network was > shut down about ten years ago. Our CDMA network was turned off in 2008. > Right now all I can think of is GSM, and while i know it's not terribly > accurate it seems like it might be the easiest. It also might be that I've > got tunnel vision and there's a simpler solution out there. > > I would be quite happy with some sort of dedicated GSM/NTP-server box, and > there are Arduino/Raspberry Pi/Linux homebuilts for that out there, but I > have been wondering if one of the fairly common GSM USB sticks could somehow > be a time source to set the server clock? > > > > Regards, > > > > Grant > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.