Re: [time-nuts] Helmholtz Resonator and other Maintained Oscillators

  This is a very nice technical discussion ...   Ulrich     In a message dated 12/9/2017 7:31:15 PM Eastern Standard Time, t...@radio.sent.com writes:   The Q of Helmholtz resonators is derived here: https://en.wikibooks.org/wiki/Acoustics/Flow-induced_Oscillations_of_a_Helmholtz_Resonator

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

Mark... You're place really moved a foot in 48 hours? Impressive and scary! >From Tom Holmes, N8ZM > On Dec 9, 2017, at 8:19 PM, Mark Sims wrote: > > Which gets real fun with things like solid earth tides getting involved. > Lady Heather can now calculate and plot solid

[time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

Which gets real fun with things like solid earth tides getting involved. Lady Heather can now calculate and plot solid earth tides. Over the last 48 hours my place moved up/down 315 mm and gravity changed 186 microgals... and that was a rather stable period. -- > A 1

[time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

Yep, to paraphrase Bunker Hunt's "a billion dollars ain't what it used to be"... a nanosecond (or picosecond) ain't what it used to be. Things that used to be insignificant n'th order theoretical nuisances are now very real significant problems. > But it's not one-to-one as

Re: [time-nuts] Helmholtz Resonator and other Maintained Oscillators

The Q of Helmholtz resonators is derived here: https://en.wikibooks.org/wiki/Acoustics/Flow-induced_Oscillations_of_a_Helmholtz_Resonator Some Q measurements of bottles are described here: https://math.dartmouth.edu/archive/m5f10/public_html/proj/ArainGolvach.pdf -- Bill Byrom N5BB On Sat, Dec

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

Mark, > In the standards definitions that include "at sea level", the question these > days is "which sea level?". Chris, > So does that mean e.g. NIST and BIPM need to measure the acceleration at > their respective locations to within parts in 10^17 or 10^18 in order to > compare their

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

Hi If the frequency sensitivity is 1x10^-13 / G you don’t need a lot of precision in your measurement of G. The same issues apply to things like magnetic field and the rest. Bob > On Dec 9, 2017, at 4:02 PM, Chris Caudle wrote: > > On Sat, December 9, 2017 2:39 pm,

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

Hi, On 12/09/2017 10:02 PM, Chris Caudle wrote: On Sat, December 9, 2017 2:39 pm, Magnus Danielson wrote: The standard acceleration is internationally agreed at 3rd CGPM in 1901 to be 9.80665 m/s^2. So does that mean e.g. NIST and BIPM need to measure the acceleration at their respective

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

On Sat, December 9, 2017 2:39 pm, Magnus Danielson wrote: > The standard acceleration is internationally agreed at 3rd CGPM in 1901 > to be 9.80665 m/s^2. So does that mean e.g. NIST and BIPM need to measure the acceleration at their respective locations to within parts in 10^17 or 10^18 in order

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

Hi, On 12/09/2017 09:13 PM, Bob kb8tq wrote: Hi I suspect that at the practical level, you define standard atmospheric pressure, standard gravity, standard magnetic field ….. and on down the list. At some point “sea level” becomes a redundant expression. The standard acceleration is

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

Hi I suspect that at the practical level, you define standard atmospheric pressure, standard gravity, standard magnetic field ….. and on down the list. At some point “sea level” becomes a redundant expression. Bob > On Dec 9, 2017, at 2:14 PM, Mark Sims wrote: > > In

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

On 12/9/17 11:14 AM, Mark Sims wrote: In the standards definitions that include "at sea level", the question these days is "which sea level?". As ocean temperature changes sea level will change (except maybe in Washington DC). Will the standards be amended to include something like "at sea

[time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

In the standards definitions that include "at sea level", the question these days is "which sea level?". As ocean temperature changes sea level will change (except maybe in Washington DC). Will the standards be amended to include something like "at sea level in 1990" or will the value being

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

Hi If you dig back into the various papers on the subject (and the proceedings that log the post paper questions) the issue of “can we trust the implementation?” does indeed come up. It’s come up for at least the last 50 years that I’m aware of. The basic argument runs that for fundamental

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

So we leave the scientific considerations and delve into the philosophical basis.  Somewhere down the line, a standard has to be established, to which all others can be compared.  How good this standard is doesn't matter, as long as it's stable.  But how does one measure stability?  Against

Re: [time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

There is a piece missing for me in the articles I have found on new atomic standards. This is what I (think I) do understand: Quantum properties of the atoms can be interrogated using various RF or optical means to servo the frequency of an oscillator (which could be a laser based optical

Re: [time-nuts] General Radio Model 723D Precision Oscillator (Tuning Fork)

Well we are kicking butt on 723 oscillators. I have the 1000 hz model and found it at the MIT flea about June. Bad rectifier section. Cap was good though I carefully reformed it. Have to say what attracted me was the case and then the realization of what it was. It works very well so now I can

Re: [time-nuts] General Radio Model 723D Precision Oscillator (Tuning Fork)

Another fascinating tuning-fork standard was used together with a Synchronome to govern the timing of pulses of Morse code on undersea telegraph cables in the British empire’s globe-girdling telegraph network. Timing was derived electromagnetically from incoming Morse code signals (a bi-polar

Re: [time-nuts] General Radio Model 723D Precision Oscillator (Tuning Fork)

Thank you, Pete.   -Don == On Sat, 2017-12-09 at 05:57 -0800, Pete Lancashire wrote: > Here's a look at a 723-C (1,000 cps) and how its power supply cap was > handled and a good look inside > > https://www.eevblog.com/forum/reviews/vintage-teardown-general-radio- >

Re: [time-nuts] General Radio Model 723D Precision Oscillator (Tuning Fork)

Here's a look at a 723-C (1,000 cps) and how its power supply cap was handled and a good look inside https://www.eevblog.com/forum/reviews/vintage-teardown-general-radio-723-c-vacuum-tube-tuning-fork/ The GR Experimenter

[time-nuts] General Radio Model 723D Precision Oscillator (Tuning Fork)

> I was fortunate to find a vintage, General Radio (GR) Model 723D > Precision Oscillator (tuning fork). > > The exceptional wooden case is as 'exciting' to look at as is the > mechanical tuning fork inside (400Hz). > > As it is ac powered, I'll need to recap it before I turn it on. >  Then, we