[time-nuts] Re: Project Great

[Lux, Jim]

On 11/28/21 8:03 PM, Tom Van Baak wrote:

Jim,

For state of the art numbers and plots, here's a recent (2020) paper:

"A Review of Contemporary Atomic Frequency Standards",
by Bonnie Schmittberger, David Scherer
https://arxiv.org/abs/2004.09987
https://arxiv.org/pdf/2004.09987.pdf

It also has plots comparing clock stability vs. size and vs. power. 
Highly recommended reading.


There is also a power point version with similar content as the paper:

https://www.gps.gov/cgsic/meetings/2019/scherer.pdf

/tvb


On 11/28/2021 2:05 PM, Lux, Jim wrote:
Speaking of which, does anyone have a link to a "current state of the 
art" graph. 

___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe 
send an email to time-nuts-le...@lists.febo.com

To unsubscribe, go to and follow the instructions there.



Awesome, these are a good start.

It's nice to have a figure to put in to reports and presentations.  
(Larry Young, recently retired from JPL who is a GNSS guru, had a hand 
drawn graph that he'd update over the years pasted into his notebook)


DSAC is shown as 10 liters (which is about how big it actually is) - I 
remember when John Prestage was talking about the 1 liter atomic clock 
more than 10 years ago, but that's the size of the physics package on 
the bench, and comparing to USOs.  That was before it was "flight ready".

___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Project Great

[Tom Van Baak]

Jim,

For state of the art numbers and plots, here's a recent (2020) paper:

"A Review of Contemporary Atomic Frequency Standards",
by Bonnie Schmittberger, David Scherer
https://arxiv.org/abs/2004.09987
https://arxiv.org/pdf/2004.09987.pdf

It also has plots comparing clock stability vs. size and vs. power. 
Highly recommended reading.


There is also a power point version with similar content as the paper:

https://www.gps.gov/cgsic/meetings/2019/scherer.pdf

/tvb


On 11/28/2021 2:05 PM, Lux, Jim wrote:
Speaking of which, does anyone have a link to a "current state of the 
art" graph. 

___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Lowest noise (phase noise and ADEV) method to achieve 10 MHz signal from 5 MHz input

[Matt Huszagh]

Hi,

I've got a 10 MHz distribution amplifier and am considering purchasing a
5 MHz reference. Most (not all) of my equipment accepts a 5 MHz
reference, but I'd like to be able to use the existing distribution
amplifier I have if possible. Therefore, I'm considering ways I might
generate a low-noise 10 MHz signal from the 5 MHz reference.

An obvious way is to use a doubler. However, as I understand it, even an
ideal doubler will add 20log(2)=6 dB of phase noise to the 10 MHz
signal. It seems like a possibly more expensive, but lower noise way
would be to use a PLL with a divider that locks the divided 10 MHz
signal to the 5 MHz input. If the time constant of the loop filter is
set long enough, does this avoid the phase noise multiplication issue?
>From what I've gathered, this is a technique HP used in some of their
gear. For example, the 8566 and 8340/1 lock a 100 MHz VCXO to an
external reference with a PLL.

Any other thoughts on this?
Matt
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Seeking advice: Is this the right way to check very short term (below 1s) stability?

[Andy Talbot]

I forgot the URL
http://g4jnt.com/10MHzDist.pdf

Andy
www.g4jnt.com



On Sun, 28 Nov 2021 at 18:39, Andy Talbot  wrote:

> The way I look at short term stability is to multiply up to microwave
> frequencies then mix the two and look at the resulting beat note.   The
> popular ADF4351 Fract-N synthesizer is ideal for this.  Take two of them,
> and programme for two frequencies in the GHz region a 1kHz or so apart when
> driven by the two 10MHz freqs that are being comparedApply the two
> multiplied signals to a mixer, and look at the resulting IF product with a
> PC soundcard input.   Using spectral analysis software with a waterfall
> display, such as Spectran or Spectrum Lab you can look at the multiplied
> frequency instability in real time.
>
> An example of the techniques used on a range of 10MHz reference sources
> can be found here (I used a different Fract-N synth with a smaller setting
> grid possible than the ADF4351 can give, but the same idea applies)
>
>
> Andy
> www.g4jnt.com
>
>
>
> On Sun, 28 Nov 2021 at 18:19, Erik Kaashoek  wrote:
>
>> As the collection of frequency sources and counters in my home lab is
>> growing I'd like to understand the performance of the frequency sources.
>> Two different GPSDO do help to check long term stability.
>> But the Rubidium frequency standard I have (Accubeat AR60A) is fairly
>> unknown and seemingly not of good reputation, more specifically its
>> (very) short term stability is doubted.
>> So how best to check very short term  (below 1s) frequency stability.
>> The frequency counters available loose resolution quickly when the gate
>> time is reduced below 1 second and high performance phase noise
>> measurement equipment is not available so google helped with a search
>> for alternative measurement methods.
>> What I found was a method using two frequency sources, one of the two
>> being  a VCO, a mixer and some filters and amplifiers.
>> By weak locking (large time constant)  the VCO source using the mixer as
>> phase detector to the other source, the output of the mixer's IF port
>> should carry a voltage real time proportionally to the phase difference
>> and by filtering and amplifying it should be possible to check for
>> variations in the 1ms-1s range.
>> Maybe even a scope can see the variations.
>> When you know the amplification and the full range voltage you can even
>> do an absolute measurement.
>> Would this method work?
>> Any specific concerns to take note of when doing the measurement?
>> Removing the DC component (or locking the VCO such that there is no DC
>> component) will be crucial I guess but given the slow speed of the loop
>> even an ADC->computer->DAC->VCO setup can work.
>> Any suggestion is welcome.
>> Erik.
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
>> send an email to time-nuts-le...@lists.febo.com
>> To unsubscribe, go to and follow the instructions there.
>
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] HP 5065A, no 2nd harmonic.

[cdelect]

With that offset either the oven set point has changed or there has een a
component value shift in the oscillator circuit. 

The easiest way to test is to stick in another 10811 if available.

You could also install one of the original  105 style oscillators if you
have one.

Cheers,

Corby
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Project Great

[Marek Doršic]

Hi,

I'm also one of those fascinated by Project Great and this was The project 
inspired me to start with time related stuf.

Can Cs clock be avoided by prolonged period at high altitudes? Assume you can 
spend a month at the summit. Is e.g. the Rb drift stable enought to compensate 
and obtain viable results?

  .marek

> On 28 Nov 2021, at 21:39, Gerhard Hoffmann  
> wrote:
> 
> 
> 
> Am 28.11.21 um 18:37 schrieb Bernd Neubig:
>> -Jim wrote-
>> I wouldn't actually think there's a Cs on ISS.  What purpose would it serve? 
>>  We as time-nuts think "of course you'd have a precise source of time", but 
>> really, there's not much need for timing on ISS on a scale smaller than 
>> seconds, if that.  NTP to timestamp files, for instance.
>> You are probaly right about the actual situation. However there is the ESA 
>> ACES project idling since years without being launched yet:
>> "ACES is an ESA ultra-stable clock experiment, a time and frequency mission 
>> to be flown on the Columbus module of the ISS (International Space Station), 
>> in support of fundamental physics tests. The mission objectives are both 
>> scientific and technological and is of great interest to two main scientific 
>> communities:
>> • The Time and Frequency (T) community; which aims to use ACES as a tool 
>> for high precision Time and Frequency metrology
>> • The Fundamental Physics community; which will benefit from the use of ACES 
>> data for accurate tests of general relativity.
>> See https://earth.esa.int/web/eoportal/satellite-missions/i/iss-aces
>> The ACES development was initiated in the 1990s. However, the decision to 
>> complete the development of the project has been achieved only at the ESA 
>> council at Ministerial Level of November 2008.
>> The launch was planned in 2018, but,  
> 
> at first 2012, completely out of touch with the world.
> 
>> as said, the clock ensemble (which BTW includes two AXTAL OCXO 100 MHz) is 
>> still sitting on the test bench and waiting and waiting.
> 
> And I can say that the AXTALs simply sat there and worked, a
> great exception for this project.
> 
> I did a redesign of the analog part of the DMTD system between
> the H-Maser and the Cs that was accepted about 7 years ago,
> the time stretcher for photon flight time interpolation, a VHDL
> triple redundancy library that looked like std_logic/vector
> and that had the redundany mostly invisibly under the hood
> (we were not given the Xilinx tools), FPGA configuration memory
> scrubbing, SEU protection of the CPU, microwave link; constantly
> filling the voids by colleges who left.
> 
> Adventures of a freelancer.
> 
> Cheers,
> Gerhard, DK4XP
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com 
>  -- To unsubscribe send an email to 
> time-nuts-le...@lists.febo.com 
> To unsubscribe, go to and follow the instructions there.

___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Project Great

[Lux, Jim]

On 11/28/21 9:37 AM, Bernd Neubig wrote:

-Jim wrote-

I wouldn't actually think there's a Cs on ISS.  What purpose would it serve?  We as 
time-nuts think "of course you'd have a precise source of time", but really, 
there's not much need for timing on ISS on a scale smaller than seconds, if that.  NTP to 
timestamp files, for instance.

You are probaly right about the actual situation. However there is the ESA ACES 
project idling since years without being launched yet:
"ACES is an ESA ultra-stable clock experiment, a time and frequency mission to 
be flown on the Columbus module of the ISS (International Space Station), in support 
of fundamental physics tests. The mission objectives are both scientific and 
technological and is of great interest to two main scientific communities:
• The Time and Frequency (T) community; which aims to use ACES as a tool for 
high precision Time and Frequency metrology
• The Fundamental Physics community; which will benefit from the use of ACES 
data for accurate tests of general relativity.

See https://earth.esa.int/web/eoportal/satellite-missions/i/iss-aces

The ACES development was initiated in the 1990s. However, the decision to 
complete the development of the project has been achieved only at the ESA 
council at Ministerial Level of November 2008.
The launch was planned in 2018, but,  as said, the clock ensemble (which BTW 
includes two AXTAL OCXO 100 MHz) is still sitting on the test bench and waiting 
and waiting.

B



Right now, for high performance in space, trapped mercury ion clocks 
seem to be the ticket.  Deep Space Atomic Clock is working well, and 
there's a DSAC2 in the works.


A fundamental problem for this kind of thing is that "infrastructure" 
(faster communications, better time) doesn't get a lot of support unless 
it enables answering a science question that the community as a whole 
deems important. In the case of NASA, it's the decadal studies that 
drive a lot (Astrophysics 2020 just came out)- The decadal study says 
"it is of great interest to answer question X" and if your technology 
helps with that, great, it might get flown.


Good independent time keeping in deep space is an enabling technology 
for autonomous navigation and rendezvous, for which there hasn't yet 
been a really compelling science need.  Perhaps when we need to do 
auto-nav around moons of planets or something like that.


For all that NASA does human exploration, it all is in service of 
answering some science question. So NASA doesn't really spend a big 
amount on problems like "how do you allow a dozen astronauts on the Moon 
to know where they are" - sure, they do studies (I've participated in 
some), they keep up on current technology, but they're not going to 
invest $100-500M in building a Position, Nav, Timing infrastructure - 
that's viewed more as an "operational thing" to "be done by others".  
Everyone sort of assumes that something with GPS-like performance will 
be available if needed, one just needs to write the check.


I'm basically a radio and computer guy at heart, so to me, one of the 
things which good timekeeping (and PNT in general) enables is large 
distributed RF sensors - radio telescopes/interferometers in space. 
Large physical extent (with precise knowledge of time and position) 
gives you good angular resolution   Precision metrology also lets you do 
things like GRACE and GRAIL - measuring the gravitational field of a 
body by measuring the distance between paired orbiters - that distance 
is measured by, you guessed it, RF and optical links, based on 
ultrastable oscillators.  Things like mercury ion clocks have the 
potential to replace USOs - and just like in terrestrial timekeeping, 
standards that rely on the fundamental physics are desirable over "fine 
artisanal craftsmanship" which is what quartz clocks are - you start 
with 1000 blanks, pick the best, mount them, pick the best, age them, 
pick the best.  And the whole time you pray that you didn't "lose the 
recipe".  USOs (and atomic clocks) are invaluable for radio science and 
gravity experiments - precisely measuring the orbit of something a long 
ways away, or sending phase coherent signals at different frequencies to 
a receiver and measuring the relative amplitude and phase for 
occultations, or just the interplanetary medium - You want something 
that has really good ADEV at tau>1000 seconds, because integration time 
is important, for both the radio science and the ranging/gravity science.


This is part of why I got selected to be project manager for SunRISE - a 
10km scale interferometer in space.  I know how these kinds of things 
work, or, even better, I know when and where to go ask questions, so I 
know what I don't know.  What I don't get to do as PM (and is somewhat 
frustrating) is design the system that does it. (The phrase from the JPL 
Chief Engineer, Rob Manning, is "When you become a manager you give up 
your SME card")

[time-nuts] Re: Seeking advice: Is this the right way to check very short term (below 1s) stability?

[Andy Talbot]

The way I look at short term stability is to multiply up to microwave
frequencies then mix the two and look at the resulting beat note.   The
popular ADF4351 Fract-N synthesizer is ideal for this.  Take two of them,
and programme for two frequencies in the GHz region a 1kHz or so apart when
driven by the two 10MHz freqs that are being comparedApply the two
multiplied signals to a mixer, and look at the resulting IF product with a
PC soundcard input.   Using spectral analysis software with a waterfall
display, such as Spectran or Spectrum Lab you can look at the multiplied
frequency instability in real time.

An example of the techniques used on a range of 10MHz reference sources can
be found here (I used a different Fract-N synth with a smaller setting grid
possible than teh ADF4351 can give, but the same idea applies)


Andy
www.g4jnt.com



On Sun, 28 Nov 2021 at 18:19, Erik Kaashoek  wrote:

> As the collection of frequency sources and counters in my home lab is
> growing I'd like to understand the performance of the frequency sources.
> Two different GPSDO do help to check long term stability.
> But the Rubidium frequency standard I have (Accubeat AR60A) is fairly
> unknown and seemingly not of good reputation, more specifically its
> (very) short term stability is doubted.
> So how best to check very short term  (below 1s) frequency stability.
> The frequency counters available loose resolution quickly when the gate
> time is reduced below 1 second and high performance phase noise
> measurement equipment is not available so google helped with a search
> for alternative measurement methods.
> What I found was a method using two frequency sources, one of the two
> being  a VCO, a mixer and some filters and amplifiers.
> By weak locking (large time constant)  the VCO source using the mixer as
> phase detector to the other source, the output of the mixer's IF port
> should carry a voltage real time proportionally to the phase difference
> and by filtering and amplifying it should be possible to check for
> variations in the 1ms-1s range.
> Maybe even a scope can see the variations.
> When you know the amplification and the full range voltage you can even
> do an absolute measurement.
> Would this method work?
> Any specific concerns to take note of when doing the measurement?
> Removing the DC component (or locking the VCO such that there is no DC
> component) will be crucial I guess but given the slow speed of the loop
> even an ADC->computer->DAC->VCO setup can work.
> Any suggestion is welcome.
> Erik.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
> an email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Lucent 849143995

[kyrrin]

    The 2100, normally, supplies +5V bias. It can be modified to do 
+12V, though it's tricky.


    +5 is a safe bet for most antennas. If the Lucent unit was made in 
the 90's-early 00's, you should be fine (I don't have any data on that 
specific number, though).


    Keep the peace(es).


On 28-Nov-21 08:50, Martin Flynn wrote:

Hi Folks,

Would like to donate an external GPS antenna for the TS2100 at the 
local radio astronomy site.


Anyone know what voltage the Lucent 849143995 GPS antenna is and if 
it's suitable for the TS2100?


Martin A Flynn / W2RWJ
Computer Deconstruction Laboratory
2201 Marconi Road
Wall Township, NJ 07719
Tel: +01 732-456-5001
Email: martin.fl...@compdecon.org
Online: www.compdecon.org
Facebook: https://www.facebook.com/compdecon/
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe 
send an email to time-nuts-le...@lists.febo.com

To unsubscribe, go to and follow the instructions there.


--
Bruce Lane, ARS KC7GR
kyr...@bluefeathertech.com
"Quando Omni Flunkus Moritati" (Red Green)
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Seeking advice: Is this the right way to check very short term (below 1s) stability?

[Bob kb8tq]

Hi

The AR-60A is a pretty good “telecom” grade Rb. Depending on which one
you have it will have a 1 second ADEV in the 5x10^-12 (rare) to 1.5x10^-11 
range. 

Once you get inside the 1 second range on any Rb, the ADEV is going to be
dominated by the OCXO in the device. The telecom grade units are rarely 
targeted at super duper low phase noise. 

In any setup that compares A to B and gives you a result, the numbers will
be dominated by the performance of the worse of the two devices. VCO’s
rarely have good ADEV …..

Bob

> On Nov 28, 2021, at 1:19 PM, Erik Kaashoek  wrote:
> 
> As the collection of frequency sources and counters in my home lab is growing 
> I'd like to understand the performance of the frequency sources.
> Two different GPSDO do help to check long term stability.
> But the Rubidium frequency standard I have (Accubeat AR60A) is fairly unknown 
> and seemingly not of good reputation, more specifically its (very) short term 
> stability is doubted.
> So how best to check very short term  (below 1s) frequency stability. The 
> frequency counters available loose resolution quickly when the gate time is 
> reduced below 1 second and high performance phase noise measurement equipment 
> is not available so google helped with a search for alternative measurement 
> methods.
> What I found was a method using two frequency sources, one of the two being  
> a VCO, a mixer and some filters and amplifiers.
> By weak locking (large time constant)  the VCO source using the mixer as 
> phase detector to the other source, the output of the mixer's IF port should 
> carry a voltage real time proportionally to the phase difference and by 
> filtering and amplifying it should be possible to check for variations in the 
> 1ms-1s range.
> Maybe even a scope can see the variations.
> When you know the amplification and the full range voltage you can even do an 
> absolute measurement.
> Would this method work?
> Any specific concerns to take note of when doing the measurement?
> Removing the DC component (or locking the VCO such that there is no DC 
> component) will be crucial I guess but given the slow speed of the loop even 
> an ADC->computer->DAC->VCO setup can work.
> Any suggestion is welcome.
> Erik.
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
> email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Seeking advice: Is this the right way to check very short term (below 1s) stability?

[Erik Kaashoek]

As the collection of frequency sources and counters in my home lab is 
growing I'd like to understand the performance of the frequency sources.

Two different GPSDO do help to check long term stability.
But the Rubidium frequency standard I have (Accubeat AR60A) is fairly 
unknown and seemingly not of good reputation, more specifically its 
(very) short term stability is doubted.
So how best to check very short term  (below 1s) frequency stability. 
The frequency counters available loose resolution quickly when the gate 
time is reduced below 1 second and high performance phase noise 
measurement equipment is not available so google helped with a search 
for alternative measurement methods.
What I found was a method using two frequency sources, one of the two 
being  a VCO, a mixer and some filters and amplifiers.
By weak locking (large time constant)  the VCO source using the mixer as 
phase detector to the other source, the output of the mixer's IF port 
should carry a voltage real time proportionally to the phase difference 
and by filtering and amplifying it should be possible to check for 
variations in the 1ms-1s range.

Maybe even a scope can see the variations.
When you know the amplification and the full range voltage you can even 
do an absolute measurement.

Would this method work?
Any specific concerns to take note of when doing the measurement?
Removing the DC component (or locking the VCO such that there is no DC 
component) will be crucial I guess but given the slow speed of the loop 
even an ADC->computer->DAC->VCO setup can work.

Any suggestion is welcome.
Erik.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Project Great

[Bernd Neubig]

-Jim wrote-

I wouldn't actually think there's a Cs on ISS.  What purpose would it serve?  
We as time-nuts think "of course you'd have a precise source of time", but 
really, there's not much need for timing on ISS on a scale smaller than 
seconds, if that.  NTP to timestamp files, for instance.

You are probaly right about the actual situation. However there is the ESA ACES 
project idling since years without being launched yet:
"ACES is an ESA ultra-stable clock experiment, a time and frequency mission to 
be flown on the Columbus module of the ISS (International Space Station), in 
support of fundamental physics tests. The mission objectives are both 
scientific and technological and is of great interest to two main scientific 
communities:
• The Time and Frequency (T) community; which aims to use ACES as a tool for 
high precision Time and Frequency metrology
• The Fundamental Physics community; which will benefit from the use of ACES 
data for accurate tests of general relativity.

See https://earth.esa.int/web/eoportal/satellite-missions/i/iss-aces

The ACES development was initiated in the 1990s. However, the decision to 
complete the development of the project has been achieved only at the ESA 
council at Ministerial Level of November 2008.
The launch was planned in 2018, but,  as said, the clock ensemble (which BTW 
includes two AXTAL OCXO 100 MHz) is still sitting on the test bench and waiting 
and waiting.

Best regards
Bernd

___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Lucent 849143995

[Martin Flynn]

Hi Folks,

Would like to donate an external GPS antenna for the TS2100 at the local 
radio astronomy site.


Anyone know what voltage the Lucent 849143995 GPS antenna is and if it's 
suitable for the TS2100?


Martin A Flynn / W2RWJ
Computer Deconstruction Laboratory
2201 Marconi Road
Wall Township, NJ 07719
Tel: +01 732-456-5001
Email: martin.fl...@compdecon.org
Online: www.compdecon.org
Facebook: https://www.facebook.com/compdecon/
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] HP 5065A on ebay

[ew via time-nuts]

Two HP 5065A on ebay in Germany                        Bert Kehren
 https://www.ebay.com/itm/353785283417?hash=item525f3f0359:g:~GkAAOSwNgZhoODS 
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Project Great

[Lux, Jim]

On 11/28/21 2:11 AM, Andy Talbot wrote:

I would imagine there are already several caesium clocks on board the ISS,
anyway.
Don't forget there is a velocity component in relativistic time shift, as
well as gravitational, so using a moving platform like an aircraft or the
ISS complicated things a lot

Andy
www.g4jnt.com

I wouldn't actually think there's a Cs on ISS.  What purpose would it 
serve?  We as time-nuts think "of course you'd have a precise source of 
time", but really, there's not much need for timing on ISS on a scale 
smaller than seconds, if that.  NTP to timestamp files, for instance.


As a practical matter, there's not a lot of "infrastructure" on ISS, 
i.e. there's no "house 10 MHz" - the experiments tend to be self 
contained.  When I was working on SCaNTestbed, which launched to ISS in 
2012, there wasn't even an onboard real-time GNSS time/position feed. We 
had a software GPS receiver as part of the testbed.  What you would get 
is a "playback" of ground predicts done by GSFC Flight Dynamics for 
position and time over MIL-STD-1553 as part of Broadcast Ancillary 
Data.  And knowing precisely where you are on ISS is tricky anyway - 
it's the size of a football stadium and flexes and moves on the scale of 
meters. The BAD data was for some presumed "center of mass", as I recall.

___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Project Great

[Lux, Jim]

On 11/27/21 11:08 PM, Tom Van Baak wrote:

Hi Thomas,

Good to hear the experiment was contagious for you. If you have 
additional questions let me know.


Your suggestion about Mount Evans and Pikes Peak are excellent. You 
will enjoy this 2017 paper:


"An Undergraduate Test of Gravitational Time Dilation"
https://arxiv.org/abs/1710.07381
https://arxiv.org/pdf/1710.07381.pdf

---

As for CSAC, the news is not so good. I've worked with several groups 
to explore CSAC for gravitational time dilation experiments. Those 
clocks are so cute and small, it's irresistible; but the numbers just 
don't add up. Over a day their stability is in the low e-12's vs. a 
"real" cesium clock like a 5071A in the low e-14's. So when you are 
doing a relativity experiment trying to detect a frequency shift 
that's on the order of e-13's you reach for a 5071A instead of a CSAC. 
The performance is nearly 100 to 1.


One solution is a taller mountain. The best on the planet is Mauna Kea 
(Big Island, Hawaii) where you can literally drive from sea level to 
the summit (13,800 ft, 4200 m) in a few hours. The frequency shift up 
there is 4.5e-13, which is 40 ns per day. But still, to have even the 
slightest chance of success you'd want your clocks to be good to 1e-13 
or better. CSAC aren't even close, and probably neither are telecom Rb.


I'm currently involved with another solution -- a HAB (High Altitude 
Balloon) CSAC flight. Getting to 100,000 ft altitude is quite common. 
Up there, clocks run a whopping 3.3e-12 faster, which is 280 ns/day, 
or 12 ns/hour. This is a clear case where the amazing low mass and low 
power of a CSAC is a  critical advantage. However, the numbers still 
aren't working out and the logistic and environmental conditions are 
brutal. I won't say it's impossible, but it may take years and a huge 
bag of tricks before it works or it's proved too impractical.


---

Jim, I'd be interested in any Cubesat / CSAC results. They don't 
exactly land in one piece so the typical round-trip clock comparison 
method wouldn't work. A direct frequency comparison might. In that 
case the drift and re-trace specs of a CSAC are probably more 
important than the stability.


/tvb



The CHOMPTT folks were trying to do time transfer using optical, but 
they also flew a CSAC (maybe even two).   One problem is that "what do 
you compare to", as you noted.  One could compare to on board GPS 1pps 
or to an onboard OCXO.  Both the CSAC and the OCXO would speed up 
relative to surface. But you also have the velocity problem (7 km/s) so 
they "apparently" run slow.  I don't know that CSAC vs GPS would 
actually be able to do the measurement - the uncertainty in the GPS is 
perhaps too high.  Maybe with post processed GPS - GIPSYX/RTGx should 
give you position and time to <1ns.


___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Re: Project Great

[Wilko Bulte]

Being curious here: has anyone ever taken a Cs in a submarine? E.g. the 
Marianatrench or so?

As a native from a mountain-deprived country I could not help wondering.

Wilko

> On 28 Nov 2021, at 08:14, Tom Van Baak  wrote:
> 
> Hi Thomas,
> 
> Good to hear the experiment was contagious for you. If you have additional 
> questions let me know.
> 
> Your suggestion about Mount Evans and Pikes Peak are excellent. You will 
> enjoy this 2017 paper:
> 
> "An Undergraduate Test of Gravitational Time Dilation"
> https://arxiv.org/abs/1710.07381
> https://arxiv.org/pdf/1710.07381.pdf
> 
> ---
> 
> As for CSAC, the news is not so good. I've worked with several groups to 
> explore CSAC for gravitational time dilation experiments. Those clocks are so 
> cute and small, it's irresistible; but the numbers just don't add up. Over a 
> day their stability is in the low e-12's vs. a "real" cesium clock like a 
> 5071A in the low e-14's. So when you are doing a relativity experiment trying 
> to detect a frequency shift that's on the order of e-13's you reach for a 
> 5071A instead of a CSAC. The performance is nearly 100 to 1.
> 
> One solution is a taller mountain. The best on the planet is Mauna Kea (Big 
> Island, Hawaii) where you can literally drive from sea level to the summit 
> (13,800 ft, 4200 m) in a few hours. The frequency shift up there is 4.5e-13, 
> which is 40 ns per day. But still, to have even the slightest chance of 
> success you'd want your clocks to be good to 1e-13 or better. CSAC aren't 
> even close, and probably neither are telecom Rb.
> 
> I'm currently involved with another solution -- a HAB (High Altitude Balloon) 
> CSAC flight. Getting to 100,000 ft altitude is quite common. Up there, clocks 
> run a whopping 3.3e-12 faster, which is 280 ns/day, or 12 ns/hour. This is a 
> clear case where the amazing low mass and low power of a CSAC is a  critical 
> advantage. However, the numbers still aren't working out and the logistic and 
> environmental conditions are brutal. I won't say it's impossible, but it may 
> take years and a huge bag of tricks before it works or it's proved too 
> impractical.
> 
> ---
> 
> Jim, I'd be interested in any Cubesat / CSAC results. They don't exactly land 
> in one piece so the typical round-trip clock comparison method wouldn't work. 
> A direct frequency comparison might. In that case the drift and re-trace 
> specs of a CSAC are probably more important than the stability.
> 
> /tvb
> 
> 
>> On 11/27/2021 12:37 PM, Thomas Valerio wrote:
>> I think that Tom's GREAT adventure is kind of what sealed the deal making
>> me a time-nut or at least a time-nuts lurker, a lot of this stuff is still
>> little over my head, but I keep reading.
>> 
>> If anyone is inclined and has the clocks and the kids ( I don't have
>> either ), there is always Mount Evans and Pikes Peak, although you may
>> have to leave the clocks behind overnight.  Mount Evans is still on my
>> bucket list but without clocks and two or three days of time to monitor
>> them, I don't think I will be doing the Mount Evans edition of GREAT.  For
>> anyone that is flush enough to afford or can beg, borrow or steal access
>> to a Microsemi chip scale atomic clock, I think a Mount Evans edition
>> would be an awesome addition to Tom's original work.
>> 
>>Thomas Valerio
>> 
>> 
>>> For newcomers to time-nuts, Andy is asking about my DIY gravitational
>>> time dilation experiment(s).
>>> 
>>>  > What am I missing?
>>> 
>>> It looks like you used the wrong value (or wrong units) for "h".
>>> 
>>> The summit of Mt Rainier is 14411 ft (4400 m), but the highest point on
>>> Mt Rainier that is accessible by road is the Paradise visitors center at
>>> 5400 ft. Our house is at 1000 ft elevation so the net difference in
>>> elevation of the clocks was 4400 ft (1340 m).
>>> 
>>> The clock(s) on the mountain ran fast by gh/c² = 9.8 × 1340 / (3e8)² =
>>> 1.5e-13. Fast clocks gain time. We stayed for about 42 hours so the net
>>> time dilation was 42×3600 × gh/c² = 22 ns.
>>> 
>>> 
>>> 
>>> For more information see the Project G.R.E.A.T. 2005 page:
>>> 
>>> http://leapsecond.com/great2005/
>>> 
>>> Better yet, these two recent talks from 2018 and 2020 cover all 3 GREAT
>>> experiments:
>>> 
>>> 
>>> 
>>> 
>>> 
>>> Lots of time nutty photos in both of those!
>>> 
>>> /tvb
>>> 
>>> 
>>> On 11/27/2021 7:33 AM, Andy Talbot wrote:
 Just been reading your adventures with 3 Cs clocks, a mountain and 3
 kids,
 but I can't make the estimate of time dilation work out.
 You measured ~ 23ns and say it agrees with calculation
 
 The equation quoted in a related reference, for "low elevations" is
 g.h/c²
 which if you plug in g = 9.81 m/s²  and h = 4300m for Mt Rainer gives
 an
 expected 

[time-nuts] Re: Frequency Standard - Where Can I Get One.

[Norman Reitz via time-nuts]

Hi Bob,
thx a lot. Now I can keep it on my list and try to get it on the second Hand 
market in a couple of years . Its a bit too much for my hobby budget.  I am 
only interested in the Audio frequences below 50mhz range, so GHz is not 
important at the Moment for me
Kind regards 
Norman

Gesendet von Yahoo Mail auf Android 
 
  Am So., Nov. 21, 2021 at 1:05 schrieb Bob kb8tq:   Hi

Rb standards have a finite life. Just how long that is depends a lot on how
good a job the heatsink on them did as well as the run time. They do die
of fairly normal random stuff as well. Like just about everything designed 
in the last 30 years, schematics and field repair manuals simply don’t exist. 

What to do:

Start looking for shorted caps. If voltages are ok then move on to things like
the frequency of the local oscillator. 

You can get surplus Rb’s built into functioning devices. Typical price seems 
to be in the $500 and up range. The advantage is that at least it worked when
it shipped. How long it will continue to work …. who knows ….

Bob

> On Nov 20, 2021, at 5:42 PM, Robert Garnett  wrote:
> 
> Hi,
> 
> 
> About five years ago I purchased a rubidium standard on eBay. It was an 
> Efratom.  Sadly although  The oscillator was working but it wouldn't lock.  I 
> was comparing it to a HP Z38001A which I use as the frequency standard in my 
> lab.
> 
> I tried to fix it, but I couldn't find the correct schematic so I abandoned 
> the project.
> 
> I would like some advice on where I could get a working one and how much I 
> should pay.
> 
> -- 
> Best Regards Rob Garnett
> Toongabbie Vctoria
> 0351 489484
> 0417 995 247
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
> email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.  
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

[time-nuts] Fwd: Re: Project Great

[ew via time-nuts]

If you are in Germany the Zugspitze at 2962 meter and Garmisch 700 meter would 
be perfect. Good amenities at both locations.                                   
                                                                                
                                                                                
      Bert Kehren                                                               
                                                                                
                                                                                
                                                                   

In a message dated 11/27/2021 5:12:19 PM Eastern Standard Time, 
j...@luxfamily.com writes: 
On 11/27/21 12:37 PM, Thomas Valerio wrote:
> I think that Tom's GREAT adventure is kind of what sealed the deal making
> me a time-nut or at least a time-nuts lurker, a lot of this stuff is still
> little over my head, but I keep reading.
>
> If anyone is inclined and has the clocks and the kids ( I don't have
> either ), there is always Mount Evans and Pikes Peak, although you may
> have to leave the clocks behind overnight.  Mount Evans is still on my
> bucket list but without clocks and two or three days of time to monitor
> them, I don't think I will be doing the Mount Evans edition of GREAT.  For
> anyone that is flush enough to afford or can beg, borrow or steal access
> to a Microsemi chip scale atomic clock, I think a Mount Evans edition
> would be an awesome addition to Tom's original work.
>
>    Thomas Valerio
>
I don't think a CSAC would be good enough.

Tom's experiment was 22 ns out of 42 hours or about 1.45E-13. That's 
quite a bit smaller than a CSAC adev over that period.

There's a variety of roads that go to ~12,000 ft in Colorado, about 
~10,000 in CA (Tioga Pass isn't closed yet), so you can get about 3x 
change, but still you're talking <1E-12.

Mammoth Mtn has a gondola to the top, but it's only 11,000. There may be 
a ski resort in CO that's higher.


>> For newcomers to time-nuts, Andy is asking about my DIY gravitational
>> time dilation experiment(s).
>>
>>  > What am I missing?
>>
>> It looks like you used the wrong value (or wrong units) for "h".
>>
>> The summit of Mt Rainier is 14411 ft (4400 m), but the highest point on
>> Mt Rainier that is accessible by road is the Paradise visitors center at
>> 5400 ft. Our house is at 1000 ft elevation so the net difference in
>> elevation of the clocks was 4400 ft (1340 m).
>>
>> The clock(s) on the mountain ran fast by gh/c² = 9.8 × 1340 / (3e8)² =
>> 1.5e-13. Fast clocks gain time. We stayed for about 42 hours so the net
>> time dilation was 42×3600 × gh/c² = 22 ns.
>>
>> 
>>
>> For more information see the Project G.R.E.A.T. 2005 page:
>>
>> http://leapsecond.com/great2005/
>>
>> Better yet, these two recent talks from 2018 and 2020 cover all 3 GREAT
>> experiments:
>>
>> 
>>
>> 
>>
>> Lots of time nutty photos in both of those!
>>
>> /tvb
>>
>>
>> On 11/27/2021 7:33 AM, Andy Talbot wrote:
>>> Just been reading your adventures with 3 Cs clocks, a mountain and 3
>>> kids,
>>> but I can't make the estimate of time dilation work out.
>>> You measured ~ 23ns and say it agrees with calculation
>>>
>>> The equation quoted in a related reference, for "low elevations" is
>>> g.h/c²
>>> which if you plug in g = 9.81 m/s²  and h = 4300m for Mt Rainer gives
>>> an
>>> expected value of 4.7 * 10^-16.
>>> Over 2 days, 2 * 86400s, that would be 81 ns in total, four times your
>>> value
>>>
>>> What am I missing?
>>>
>>> Was just speculating what Ben Nevis at a mere 1340m height might offer
>>>
>>> Andy
>>> www.g4jnt.com
>>> ___
>>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe
>>> send an email to time-nuts-le...@lists.febo.com
>>> To unsubscribe, go to and follow the instructions there.
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send
>> an email to time-nuts-le...@lists.febo.com
>> To unsubscribe, go to and follow the instructions there.
>>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
> email to time-nuts-le...@lists.febo.com
> To unsubscribe, go to and follow the instructions there.
>
___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow the instructions there.

___
time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an 
email to time-nuts-le...@lists.febo.com
To unsubscribe, go to and follow 

[time-nuts] Re: Project Great

[Andy Talbot]

I would imagine there are already several caesium clocks on board the ISS,
anyway.
Don't forget there is a velocity component in relativistic time shift, as
well as gravitational, so using a moving platform like an aircraft or the
ISS complicated things a lot

Andy
www.g4jnt.com



On Sun, 28 Nov 2021 at 10:03, Dave ZL3FJ <2c...@silverbears.nz> wrote:

> Is the ISS a suitable platform?
> I expect getting the experiment package on there would be quite another
> matter!
> DaveB, NZ
>
>
> -Original Message-
> From: Tom Van Baak [mailto:t...@leapsecond.com]
> Sent: Sunday, November 28, 2021 20:09
> To: time-nuts@lists.febo.com
> Subject: [time-nuts] Re: Project Great
>
> Hi Thomas,
>
> Good to hear the experiment was contagious for you. If you have additional
> questions let me know.
>
> Your suggestion about Mount Evans and Pikes Peak are excellent. You will
> enjoy this 2017 paper:
>
> "An Undergraduate Test of Gravitational Time Dilation"
> https://arxiv.org/abs/1710.07381
> https://arxiv.org/pdf/1710.07381.pdf
>
> ---
>
> As for CSAC, the news is not so good. I've worked with several groups to
> explore CSAC for gravitational time dilation experiments. Those clocks are
> so cute and small, it's irresistible; but the numbers just don't add up.
> Over a day their stability is in the low e-12's vs. a "real" cesium clock
> like a 5071A in the low e-14's. So when you are doing a relativity
> experiment trying to detect a frequency shift that's on the order of e-13's
> you reach for a 5071A instead of a CSAC. The performance is nearly 100 to 1.
>
> One solution is a taller mountain. The best on the planet is Mauna Kea
> (Big Island, Hawaii) where you can literally drive from sea level to the
> summit (13,800 ft, 4200 m) in a few hours. The frequency shift up there is
> 4.5e-13, which is 40 ns per day. But still, to have even the slightest
> chance of success you'd want your clocks to be good to 1e-13 or better.
> CSAC aren't even close, and probably neither are telecom Rb.
>
> I'm currently involved with another solution -- a HAB (High Altitude
> Balloon) CSAC flight. Getting to 100,000 ft altitude is quite common. Up
> there, clocks run a whopping 3.3e-12 faster, which is 280 ns/day, or 12
> ns/hour. This is a clear case where the amazing low mass and low power of a
> CSAC is a  critical advantage. However, the numbers still aren't working
> out and the logistic and environmental conditions are brutal. I won't say
> it's impossible, but it may take years and a huge bag of tricks before it
> works or it's proved too impractical.
>
> ---
>
> Jim, I'd be interested in any Cubesat / CSAC results. They don't exactly
> land in one piece so the typical round-trip clock comparison method
> wouldn't work. A direct frequency comparison might. In that case the drift
> and re-trace specs of a CSAC are probably more important than the stability.
>
> /tvb
>
>
> On 11/27/2021 12:37 PM, Thomas Valerio wrote:
> > I think that Tom's GREAT adventure is kind of what sealed the deal
> > making me a time-nut or at least a time-nuts lurker, a lot of this
> > stuff is still little over my head, but I keep reading.
> >
> > If anyone is inclined and has the clocks and the kids ( I don't have
> > either ), there is always Mount Evans and Pikes Peak, although you may
> > have to leave the clocks behind overnight.  Mount Evans is still on my
> > bucket list but without clocks and two or three days of time to
> > monitor them, I don't think I will be doing the Mount Evans edition of
> > GREAT.  For anyone that is flush enough to afford or can beg, borrow
> > or steal access to a Microsemi chip scale atomic clock, I think a
> > Mount Evans edition would be an awesome addition to Tom's original work.
> >
> > Thomas Valerio
> >
> >
> >> For newcomers to time-nuts, Andy is asking about my DIY gravitational
> >> time dilation experiment(s).
> >>
> >>   > What am I missing?
> >>
> >> It looks like you used the wrong value (or wrong units) for "h".
> >>
> >> The summit of Mt Rainier is 14411 ft (4400 m), but the highest point
> >> on Mt Rainier that is accessible by road is the Paradise visitors
> >> center at
> >> 5400 ft. Our house is at 1000 ft elevation so the net difference in
> >> elevation of the clocks was 4400 ft (1340 m).
> >>
> >> The clock(s) on the mountain ran fast by gh/c² = 9.8 × 1340 /
> >> (3e8)² = 1.5e-13. Fast clocks gain time. We stayed for about 42
> >> hours so the net time dilation was 42×3600 × gh/c² = 22 ns.
> >>
> >> 
> >>
> >> For more information see the Project G.R.E.A.T. 2005 page:
> >>
> >> http://leapsecond.com/great2005/
> >>
> >> Better yet, these two recent talks from 2018 and 2020 cover all 3
> >> GREAT
> >> experiments:
> >>
> >>  >> -VanBaak-GPS_Flying_Clocks_and_Relativity.pdf>
> >>
> >>  >> y.pdf>
> >>
> >> Lots of time nutty photos in both of 

[time-nuts] Re: Project Great

[Dave ZL3FJ]

Is the ISS a suitable platform?
I expect getting the experiment package on there would be quite another matter!
DaveB, NZ


-Original Message-
From: Tom Van Baak [mailto:t...@leapsecond.com] 
Sent: Sunday, November 28, 2021 20:09
To: time-nuts@lists.febo.com
Subject: [time-nuts] Re: Project Great

Hi Thomas,

Good to hear the experiment was contagious for you. If you have additional 
questions let me know.

Your suggestion about Mount Evans and Pikes Peak are excellent. You will enjoy 
this 2017 paper:

"An Undergraduate Test of Gravitational Time Dilation"
https://arxiv.org/abs/1710.07381
https://arxiv.org/pdf/1710.07381.pdf

---

As for CSAC, the news is not so good. I've worked with several groups to 
explore CSAC for gravitational time dilation experiments. Those clocks are so 
cute and small, it's irresistible; but the numbers just don't add up. Over a 
day their stability is in the low e-12's vs. a "real" cesium clock like a 5071A 
in the low e-14's. So when you are doing a relativity experiment trying to 
detect a frequency shift that's on the order of e-13's you reach for a 5071A 
instead of a CSAC. The performance is nearly 100 to 1.

One solution is a taller mountain. The best on the planet is Mauna Kea (Big 
Island, Hawaii) where you can literally drive from sea level to the summit 
(13,800 ft, 4200 m) in a few hours. The frequency shift up there is 4.5e-13, 
which is 40 ns per day. But still, to have even the slightest chance of success 
you'd want your clocks to be good to 1e-13 or better. CSAC aren't even close, 
and probably neither are telecom Rb.

I'm currently involved with another solution -- a HAB (High Altitude
Balloon) CSAC flight. Getting to 100,000 ft altitude is quite common. Up there, 
clocks run a whopping 3.3e-12 faster, which is 280 ns/day, or 12 ns/hour. This 
is a clear case where the amazing low mass and low power of a CSAC is a  
critical advantage. However, the numbers still aren't working out and the 
logistic and environmental conditions are brutal. I won't say it's impossible, 
but it may take years and a huge bag of tricks before it works or it's proved 
too impractical.

---

Jim, I'd be interested in any Cubesat / CSAC results. They don't exactly land 
in one piece so the typical round-trip clock comparison method wouldn't work. A 
direct frequency comparison might. In that case the drift and re-trace specs of 
a CSAC are probably more important than the stability.

/tvb


On 11/27/2021 12:37 PM, Thomas Valerio wrote:
> I think that Tom's GREAT adventure is kind of what sealed the deal 
> making me a time-nut or at least a time-nuts lurker, a lot of this 
> stuff is still little over my head, but I keep reading.
>
> If anyone is inclined and has the clocks and the kids ( I don't have 
> either ), there is always Mount Evans and Pikes Peak, although you may 
> have to leave the clocks behind overnight.  Mount Evans is still on my 
> bucket list but without clocks and two or three days of time to 
> monitor them, I don't think I will be doing the Mount Evans edition of 
> GREAT.  For anyone that is flush enough to afford or can beg, borrow 
> or steal access to a Microsemi chip scale atomic clock, I think a 
> Mount Evans edition would be an awesome addition to Tom's original work.
>
> Thomas Valerio
>
>
>> For newcomers to time-nuts, Andy is asking about my DIY gravitational 
>> time dilation experiment(s).
>>
>>   > What am I missing?
>>
>> It looks like you used the wrong value (or wrong units) for "h".
>>
>> The summit of Mt Rainier is 14411 ft (4400 m), but the highest point 
>> on Mt Rainier that is accessible by road is the Paradise visitors 
>> center at
>> 5400 ft. Our house is at 1000 ft elevation so the net difference in 
>> elevation of the clocks was 4400 ft (1340 m).
>>
>> The clock(s) on the mountain ran fast by gh/c² = 9.8 × 1340 / 
>> (3e8)² = 1.5e-13. Fast clocks gain time. We stayed for about 42 
>> hours so the net time dilation was 42×3600 × gh/c² = 22 ns.
>>
>> 
>>
>> For more information see the Project G.R.E.A.T. 2005 page:
>>
>> http://leapsecond.com/great2005/
>>
>> Better yet, these two recent talks from 2018 and 2020 cover all 3 
>> GREAT
>> experiments:
>>
>> > -VanBaak-GPS_Flying_Clocks_and_Relativity.pdf>
>>
>> > y.pdf>
>>
>> Lots of time nutty photos in both of those!
>>
>> /tvb
>>
>>
>> On 11/27/2021 7:33 AM, Andy Talbot wrote:
>>> Just been reading your adventures with 3 Cs clocks, a mountain and 3 
>>> kids, but I can't make the estimate of time dilation work out.
>>> You measured ~ 23ns and say it agrees with calculation
>>>
>>> The equation quoted in a related reference, for "low elevations" is 
>>> g.h/c² which if you plug in g = 9.81 m/s²  and h = 4300m for Mt 
>>> Rainer gives an expected value of 4.7 * 10^-16.
>>> Over 2 days, 2 * 86400s, that would be 81 ns in