Attila Kinali <attila@kinali.ch> wrote: > Mike Cook <michael.cook@sfr.fr> wrote: > > > c. The first commercial cesium clocks were available in 1956, but the > > second did not get redefined until 1967. There is no rush. > > Which caesium beam standards were available in 1956? The Atomichron, I think: http://ieeemilestones.ethw.org/images/8/8d/Forman_Proc_IEEE_1985.pdf Tony. -- f.anthony.n.finch <dot@dotat.at> http://dotat.at/ Fair Isle: Southwest 5 or 6, becoming variable 4 later. Moderate or rough. Showers, rain later. Good, occasionally poor later.

Mike, Attila, Rick, > Which caesium beam standards were available in 1956? The Atomichron, made by the National Company. This was the first commercial cesium standard; about 50 were made. Attila, you saw one at my house when you visited last year. It's about 7 feet tall. The one I have was used by NBS(NIST), then made its way to a remote cabin in Minnesota for a couple decades, then to a garage in Minneapolis, where I bought it and drove it to Seattle. Atomichron photos here [1]. The hp 5060 and 5061 came much later. > The picture of the beam tube is only a small fraction of the clock itself. There are multiple racks full of RF equipment not shown Correct. Better views of Essen's cesium clock and laboratory here [2]. Note also the Atomichron in the background of figure 6. Since you are interested in the history of atomic clocks, especially cesium beam clocks, I highly recommend these papers: http://geodesy.unr.edu/hanspeterplag/library/geodesy/time/met5_3_S01.pdf "History of early atomic clocks" Norman F Ramsey http://geodesy.unr.edu/hanspeterplag/library/geodesy/time/met5_3_S02.pdf "Essen and the National Physical Laboratory’s atomic clock" Dale Henderson http://geodesy.unr.edu/hanspeterplag/library/geodesy/time/met5_3_S04.pdf "Atomic time-keeping from 1955 to the present" Bernard Guinot, Elisa Felicitas Arias http://geodesy.unr.edu/hanspeterplag/library/geodesy/time/met5_3_s05.pdf "The classical caesium beam frequency standard: fifty years later" Jacques Vanier, Claude Audoin http://geodesy.unr.edu/hanspeterplag/library/geodesy/time/met5_3_S10.pdf "Fifty years of commercial caesium clocks" Leonard S Cutler The above come from: https://iopscience.iop.org/issue/0026-1394/42/3 Special issue of Metrologia: “Special issue: fifty years of atomic time-keeping: 1955 to 2005”, Volume 42, Number 3, June 2005. See also: https://ieee-uffc.org/about-us/history/uffc-s-history/history-of-atomic-frequency-standards-a-trip-through-20th-century-physics/ "History of Atomic Frequency Standards: A Trip Through 20th Century Physics" Arthur O. McCoubrey https://ieee-uffc.org/about-us/history/uffc-s-history/atomichron/ "Atomichron: The Atomic Clock from Concept to Commercial Product" Paul Forman https://tycho.usno.navy.mil/ptti/1985papers/Vol%2017_01.pdf The First Atomic Clock Program: NBS, 1947-1954 Paul Forman A fine collection of clear photos and historical PDF here: <https://ethw.org/Milestones:First_Atomic_Clock,_1948> And finally, https://nvlpubs.nist.gov/nistpubs/jres/122/jres.122.029.pdf also found here: https://tf.nist.gov/general/pdf/2907.pdf or here: https://tf.nist.gov/general/pdf/2917.pdf "A Historical Review of U.S. Contributions to the Atomic Redefinition of the SI Second in 1967" Michael A. Lombardi /tvb [1] http://www.leapsecond.com/museum/nc2001/ [2] https://www.researchgate.net/publication/320878080_Two_clocks_that_changed_the_world_The_birth_of_atomic_timekeeping

2.  interesting observation: turning the unit 90 degrees onto its right

Can the shift be duplicated by an electromagnetic field? If so this may be a was to fine tune an oscillator. Glenn On 6/3/2019 6:29 PM, Adrian Godwin wrote: > On Mon, Jun 3, 2019 at 11:01 PM Andy Backus <andrewbackus@msn.com> wrote: > >> 2. interesting observation: turning the unit 90 degrees onto its right >> hand side immediately increases the output frequency by 10 mHz >> (reversible); turning the unit 90 degrees onto its left end immediately >> decreases the output frequency by 10 mHz (also reversible) >> >> > This is quite normal. > > https://www.youtube.com/watch?v=zILwgQhjC_Q > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > -- ----------------------------------------------------------------------- Glenn Little ARRL Technical Specialist QCWA LM 28417 Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178 QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license"

Hi G sensitivity in quartz crystals is a pretty well documented sort of thing. For an AT cut numbers in the 1 to 2 ppb per G are not uncommon. For SC’s the numbers may be a bit lower than that. It simply has to do with the stress / strain properties of the quartz and how they impact the resonant frequency. So no, you can’t duplicate it directly with an electromagnetic field. You can indeed tune an SC with voltage on the electrodes. Not so much with an AT. Bob > On Jun 4, 2019, at 6:32 PM, Glenn Little WB4UIV <glennmaillist@bellsouth.net> wrote: > > Can the shift be duplicated by an electromagnetic field? > If so this may be a was to fine tune an oscillator. > > Glenn > > On 6/3/2019 6:29 PM, Adrian Godwin wrote: >> On Mon, Jun 3, 2019 at 11:01 PM Andy Backus <andrewbackus@msn.com> wrote: >> >>> 2. interesting observation: turning the unit 90 degrees onto its right >>> hand side immediately increases the output frequency by 10 mHz >>> (reversible); turning the unit 90 degrees onto its left end immediately >>> decreases the output frequency by 10 mHz (also reversible) >>> >>> >> This is quite normal. >> >> https://www.youtube.com/watch?v=zILwgQhjC_Q >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > > -- > ----------------------------------------------------------------------- > Glenn Little ARRL Technical Specialist QCWA LM 28417 > Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178 > QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR > "It is not the class of license that the Amateur holds but the class > of the Amateur that holds the license" > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

More complete evaluation of the BG7TBL from eBay: One week continuously powered up. 19-23 degrees ambient temperature, 55-65% humidity. Output 10 MHz at 4 volts p-p. Frequency measured by phase drift rate when compared to a Thunderbolt GPSDO 10 MHz standard using a scope. Precision -- +/- 0.5 mHz over two days (50-200 sec runs) with the caveat that the oven seems to regulate over a 100-second cycle with a hysteresis of +/- 0.5 mHz so the "instantaneous" frequency could be +/- 1 mHz Accuracy -- limited by the resolution of the calibration pot to about +/- 1 mHz Gravity effects (looking at the front panel) -- rotation 90 degrees counter clockwise causes a 5.8 mHz decrease in frequency rotation 180 degrees causes a 5.3 mHz increase in frequency rotation 90 degrees clockwise causes a 12.5 mHz increase in frequency Andy Backus ________________________________ From: time-nuts <time-nuts-bounces@lists.febo.com> on behalf of Bernd Neubig <BNeubig@t-online.de> Sent: Monday, June 3, 2019 3:26 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] BG7TBL 10 MHz OCXO 2. interesting observation: turning the unit 90 degrees onto its right hand side immediately increases the output frequency by 10 mHz (reversible); turning the unit 90 degrees onto its left end immediately decreases the output frequency by 10 mHz (also reversible) This meant that the g-sensitivity is in the order of magnitude of 1 ppb/g which is quite a normal order of magnitude. Correctly doing the 2g-flipover would tilt the OCXO by 180° an divide the observed relative frequency change by 2. But also this simple test is not necessarily an accurate measure of the g-sensitivity. As the extremes may now occur at 180° tilt. Also care has to be taken to distinguish between the frequency shift caused by the g-sensitivity and a frequency drift (usually slower) by thermal effects, as the internal temperature profile is also reversing. Have fun Bernd DK1AG _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.