But if you think about it, 21ns... that's what they call local time. On 29 March 2010 01:48, Steve Rooke <[email protected]> wrote: > I've switched off my t'bolt. If I can't be closer than 21ns to the > correct time, it just isn't worth it. > > :) > > On 29 March 2010 01:36, Bob Camp <[email protected]> wrote: >> Hi >> >> If you get arrested for keeping your bar open 21 ns after official closing >> time, it's the USNO version you need to be "right with". The BIPM isn't >> going to help you with the judge. >> >> Bob >> >> On Mar 28, 2010, at 7:58 AM, Arnold Tibus wrote: >> >>> The answer looks to me a bit difficult reading the USNO definition : >>> >>> INTERNATIONAL TIME SCALES AND THE B.I.P.M. >>> http://tycho.usno.navy.mil/bipm.html >>> >>> citing: >>> "...the U.S. Naval Observatory timescale, UTC(USNO), >>> and its real-time implementation, Master Clock #2 (MC #2), >>> are kept within a close but unspecified tolerance of the >>> international atomic timescale published >>> by the Bureau International des Poids et Mesures >>> (International Bureau of Weights and Measures [BIPM]) >>> in Sevres, France." >>> >>> "...Hence, all these atomic timescales are called >>> Coordinated Universal Time (UTC), of which USNO's >>> version is UTC(USNO)." >>> >>> "...The difference between UTC (computed by BIPM) and any other >>> timing center's UTC only becomes known after computation and >>> dissemination of UTC, which occurs about two weeks after the fact. >>> This difference is presently limited mainly by the long-term frequency >>> instability of UTC. >>> UTC(USNO) has been kept within 26 nanoseconds of UTC during >>> the past year through frequency steering of our Master Clocks to our >>> extrapolation of UTC." >>> >>> So I do understand that BIPM is the world's time keeper, but there >>> may be a difference between the UTCs of up to 26ns? >>> >>> "...Since synchronization is never perfect, we provide the latest data >>> below on the differences between UTC and the UTC of other timing >>> centers, including USNO,..." >>> and >>> "...All of our reference clocks are real-time approximations of UTC(USNO), >>> and as such are denoted UTC(USNO,MC). Master Clock #2 (MC #2) is >>> our official reference clock..." >>> >>> So I understand this as, that the USA do refer to the time reference >>> of USNO - and the rest of the world to BIPM directly? >>> >>> Since dec. 2009 the PTB in Braunschweig, Germany (with the new >>> CSF2) and the BIPM in Sevre are the only countries running 4 of the >>> most precise primary Cs fountain clocks, if I am informed correctly. >>> Together they should run quite close to the time defined by BIPM I think, >>> and according our law our official time is transmitted by the PTB. >>> >>> Now, How do I have to interprete the readout of GPSDOs like >>> Trimble's Thunderbolt and others PPS difference in ns to UTC? >>> >>> To which UTC? I suppose to the time transmitted by the US GPS SATs. >>> Is there another difference in UTC to BIPM included? >>> What is with Glonass (and will be later perhaps with Galileo)? >>> >>> In fact the use of GPS is already spreaded all over the world and >>> in use in many technical applications, meaning that the world does >>> refer to UTC given by US GPS !? >>> >>> Does it make sense under this circumstance as Time Nut to go >>> below the Xns (26ns ?) frontier as absolute measure? >>> Will this ever be possible? (Everything is relative...) >>> >>> But excuse me in case I do miss and misunderstand something >>> fully... >>> >>> Arnold, DK2WT >>> >>> >>> On Sun, 28 Mar 2010 22:29:22 +1300, Steve Rooke wrote: >>> >>>> What puzzles me is who is the keeper of "legal time" for the other >>>> 93.4% of land mass and 95.5% of population of the World other than the >>>> US. >>> >>>> On 28 March 2010 04:49, David Forbes <[email protected]> wrote: >>>>> At 11:11 AM -0400 3/27/10, Bob Camp wrote: >>>>>> >>>>>> I would bet that if you went deep enough into the details, that the Army >>>>>> at some point was less than enthusiastic about having to ask the Navy >>>>>> when >>>>>> ever they wanted to know what time it was. >>>>> >>>>> My guess is that the Army just asked Western Union, who asked the Navy. >>>>> >>>>> -- >>>>> >>>>> --David Forbes, Tucson, AZ >>>>> http://www.cathodecorner.com/ >>>>> >>> >>> >>> >>> >>> >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > > > -- > Steve Rooke - ZL3TUV & G8KVD > A man with one clock knows what time it is; > A man with two clocks is never quite sure. >
-- Steve Rooke - ZL3TUV & G8KVD A man with one clock knows what time it is; A man with two clocks is never quite sure. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
