Hi The sawtooth issues of most GPS receivers are much greater than the position errors a short / long survey will produce. Unless you have a very fancy self correcting receiver or a driver that does sawtooth correction, don't' worry about it.
Bob On May 5, 2013, at 5:33 PM, Tom Knox <act...@hotmail.com> wrote: > The idea of a Mercury Ion clocks started about 2000 and from about 2005 until > recently has held the title of worlds most accurate clock. > Approx 1 sec per 1.6 billion years the last I heard. At the heart is a single > trapped mercury atom. Jim Bergquist at NIST was one of those that lead the > development. > This link has the basics: http://tf.nist.gov/general/pdf/1957.pdf. I want > two. > > Thomas Knox > > > 1-303-554-0307 > >> Date: Sun, 5 May 2013 06:59:12 -0700 >> From: jim...@earthlink.net >> To: time-nuts@febo.com >> Subject: [time-nuts] vs Hg ion? Re: GPS clock stabilitiy, Rb vs Cs >> >> On 5/5/13 1:48 AM, Magnus Danielson wrote: >>> On 05/05/2013 10:05 AM, Attila Kinali wrote: >>>> On Sat, 4 May 2013 12:36:20 -0700 >>>> "Tom Van Baak (lab)"<t...@leapsecond.com> wrote: >>>> >>>>> Rule of thumb: quartz is best short term, Rb or H-maser mid-term, >>>>> and Cs by far the best long-term. >>>> >>>> Ah.. so it's a fundamental limitation. And i was looking for something >>>> GPS specific. >>>> >>>> Any references i could read on those limitations? A quick google >>>> did not produce any good results. >>> >>> There is a handful of references but picking up a book like "Quantum >>> Leap" is a good start. >>> >>> Quartz is a bit of (syntetic) rock, cut at some angle(s), cleaned, >>> mounted in some hermetic sealed chamber with residue dirt, and mounting >> >> <snip> >> >>> >>> For rubidium gas-cell, there is a bunch of systematics, including >> <snip> >> >>> The caesium atomic beam does not have wall-shifts, but rather it has >>> much lower systematics. One of the major onces being magnetic field. >> <snip> >> >>> The above is a summary of things collected from a variety of sources, >>> but I think this coarse walk-through of issues gives some insight as to >>> what issues pops up where and the milage vary a lot within each group. >>> Modern high-performance rubidium gas-cells outperform the early >>> caesiums, high-performance crystals outperform several rubidiums. >>> The HP5065A is an example of an old clock with really good performance, >>> so modern is not everything, and the modern compact telecom rubidiums >>> and for that mater CSAC is more space/power oriented than ultimate >>> performance of the technology as such. >> >> >> I wonder where mercury ion fits in the scheme of things, since that's >> where we're spending some money for spacecraft applications right now. >> It's supposed to be orders of magnitude better than Rb. >> >> >> _______________________________________________ >> 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. _______________________________________________ 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.