Time Dilation tinkering
Hi,
I've been mostly lurking on the list for some time now and follow with
interest the many discussions. Very much at the early stages of my
time-nut journey, but enjoying it so far :)
I'd like to have a go at re-creating the efforts of Tom (and I gather
others) in taking a clock up a mountain for a while and seeing if I can
measure the relativistic changes.
Being based in Australia gives me a couple of challenges, for one we
don't really do mountains in the same sense as much of the rest of the
world - so the highest peak I can readily get to from Melbourne is about
1,600m ASL. I live at 80m ASL - so a delta of around 1,500m altitude
and several hundred km drive.
If I do the math correctly that's about 14ns difference per 24h the
clocks are separated by that altitude. [1]
We also lack quite the same surplus market here as the US, so purchasing
a Caesium based standard is well beyond my means.
This got me to wondering if a Rubidium based standard might do the trick
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.
Clearly there'd need to be a bunch of extra gubbins [2] added to the
10MHz standard to turn it into an actual clock/counter including battery
backup and so forth. And would need a pair of everything.
Before I delve too far into the planning, I'd be interested in feedback
as to whether this style of Rb standard is likely to be up to the task
of being the core of such an endeavour or not ?
Oh I should add - my plan was to build the systems such that they
function as nice standalone time/frequency references once this
experiment is concluded :)
Thanks in advance,
Kind Regards/73,
Hugh
VK3YYZ/AD5RV
[1] gh/c^2 x 3600 x 24 Where h is 1500, g and c the usual values :)
[2] I presume at a minimum a counter running at a 5ns or less "tick" fed
from a frequency source locked to the 10MHz of the Rb standard. This
counter would need to be latched for reading from an external signal so
that it can be compared to the second clock. Not sure but seems the
TAPR TICC might have role here :)
Hi Hugh,
If I do the math correctly that's about 14ns difference per 24h the
clocks are separated by that altitude. [1]
That's correct. For your 1500m elevation gain, the gravitational redshift, the df/f frequency change, will be about 1.6e-13. To be able to measure with any confidence you'll want your clocks to be stable to about 2e-14, at tau 1 or 2 days.
This got me to wondering if a Rubidium based standard might do the trick
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.
There are tricks and technical factors, but the main one is how stable these are at tau 1 day. Buy or borrow a few of them and see if they are mutually stable to the level required. I suspect not. But perhaps other time nuts could comment on how stable their surplus Rb are out to tau 1 day.
There are lots of other details; some to your advantage, some not. But if the surplus Rb can't perform down in the -14's at a day, even in laboratory conditions, then the rest of the discussion doesn't matter.
Yes, the TAPR TICC counter would work well for this experiment. But to be honest, any old nanosecond-level counter is good enough. I say this not to discourage you from a good excuse to buy a TICC, but to encourage you to do the ADEV math to see how clocks and counters and tau can interact in your favor.
/tvb
----- Original Message -----
From: "Hugh Blemings" hugh@blemings.org
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Sent: Monday, March 20, 2017 7:38 PM
Subject: [time-nuts] Time Dilation tinkering
Hi,
I've been mostly lurking on the list for some time now and follow with
interest the many discussions. Very much at the early stages of my
time-nut journey, but enjoying it so far :)
I'd like to have a go at re-creating the efforts of Tom (and I gather
others) in taking a clock up a mountain for a while and seeing if I can
measure the relativistic changes.
Being based in Australia gives me a couple of challenges, for one we
don't really do mountains in the same sense as much of the rest of the
world - so the highest peak I can readily get to from Melbourne is about
1,600m ASL. I live at 80m ASL - so a delta of around 1,500m altitude
and several hundred km drive.
If I do the math correctly that's about 14ns difference per 24h the
clocks are separated by that altitude. [1]
We also lack quite the same surplus market here as the US, so purchasing
a Caesium based standard is well beyond my means.
This got me to wondering if a Rubidium based standard might do the trick
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.
Clearly there'd need to be a bunch of extra gubbins [2] added to the
10MHz standard to turn it into an actual clock/counter including battery
backup and so forth. And would need a pair of everything.
Before I delve too far into the planning, I'd be interested in feedback
as to whether this style of Rb standard is likely to be up to the task
of being the core of such an endeavour or not ?
Oh I should add - my plan was to build the systems such that they
function as nice standalone time/frequency references once this
experiment is concluded :)
Thanks in advance,
Kind Regards/73,
Hugh
VK3YYZ/AD5RV
[1] gh/c^2 x 3600 x 24 Where h is 1500, g and c the usual values :)
[2] I presume at a minimum a counter running at a 5ns or less "tick" fed
from a frequency source locked to the 10MHz of the Rb standard. This
counter would need to be latched for reading from an external signal so
that it can be compared to the second clock. Not sure but seems the
TAPR TICC might have role here :)
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.
H
On Mar 21, 2017, at 4:58 AM, Tom Van Baak tvb@LeapSecond.com wrote:
Hi Hugh,
If I do the math correctly that's about 14ns difference per 24h the
clocks are separated by that altitude. [1]
That's correct. For your 1500m elevation gain, the gravitational redshift, the df/f frequency change, will be about 1.6e-13. To be able to measure with any confidence you'll want your clocks to be stable to about 2e-14, at tau 1 or 2 days.
This got me to wondering if a Rubidium based standard might do the trick
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.
There are tricks and technical factors, but the main one is how stable these are at tau 1 day. Buy or borrow a few of them and see if they are mutually stable to the level required. I suspect not. But perhaps other time nuts could comment on how stable their surplus Rb are out to tau 1 day.
There are lots of other details; some to your advantage, some not. But if the surplus Rb can't perform down in the -14's at a day, even in laboratory conditions, then the rest of the discussion doesn't matter.
An ex-telecom Rb will run a bit below 1x10^-12, but not below 1x10^-13 at tau = 1 day. Roughly speaking it’s about 10X less stable than you need. That’s in a carefully controlled temperature and pressure environment. One fake out with Rb’s is that they are pressure sensitive. You will see an impact simply from the lower pressure on the top of the mountain. How much impact varies from unit to unit. It’s a good bet you need to compensate for it well before you get to 1x10^-13 on a mountain trip.
To put this all in context, a 5071 in good condition can (barely) do this experiment by running up to a mountain top. There’s a lot of fiddly details you need to take care of even with a 5071. AFIK, Tom is the first to do it this way (Cs in the back of the family car). All previous work with older Cs standards had to go to much greater lengths to observe the effect. If you take a standard up to satellite orbit sort of altitude, you get a shift of ~1.5x10^-10. That would be fine for a number of frequency standards. It is not very practical on the transport side of the experiment.
Many options, but none of them easy.
Bob
Yes, the TAPR TICC counter would work well for this experiment. But to be honest, any old nanosecond-level counter is good enough. I say this not to discourage you from a good excuse to buy a TICC, but to encourage you to do the ADEV math to see how clocks and counters and tau can interact in your favor.
/tvb
----- Original Message -----
From: "Hugh Blemings" hugh@blemings.org
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Sent: Monday, March 20, 2017 7:38 PM
Subject: [time-nuts] Time Dilation tinkering
Hi,
I've been mostly lurking on the list for some time now and follow with
interest the many discussions. Very much at the early stages of my
time-nut journey, but enjoying it so far :)
I'd like to have a go at re-creating the efforts of Tom (and I gather
others) in taking a clock up a mountain for a while and seeing if I can
measure the relativistic changes.
Being based in Australia gives me a couple of challenges, for one we
don't really do mountains in the same sense as much of the rest of the
world - so the highest peak I can readily get to from Melbourne is about
1,600m ASL. I live at 80m ASL - so a delta of around 1,500m altitude
and several hundred km drive.
If I do the math correctly that's about 14ns difference per 24h the
clocks are separated by that altitude. [1]
We also lack quite the same surplus market here as the US, so purchasing
a Caesium based standard is well beyond my means.
This got me to wondering if a Rubidium based standard might do the trick
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.
Clearly there'd need to be a bunch of extra gubbins [2] added to the
10MHz standard to turn it into an actual clock/counter including battery
backup and so forth. And would need a pair of everything.
Before I delve too far into the planning, I'd be interested in feedback
as to whether this style of Rb standard is likely to be up to the task
of being the core of such an endeavour or not ?
Oh I should add - my plan was to build the systems such that they
function as nice standalone time/frequency references once this
experiment is concluded :)
Thanks in advance,
Kind Regards/73,
Hugh
VK3YYZ/AD5RV
[1] gh/c^2 x 3600 x 24 Where h is 1500, g and c the usual values :)
[2] I presume at a minimum a counter running at a 5ns or less "tick" fed
from a frequency source locked to the 10MHz of the Rb standard. This
counter would need to be latched for reading from an external signal so
that it can be compared to the second clock. Not sure but seems the
TAPR TICC might have role here :)
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.
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On Tue, 21 Mar 2017 13:38:51 +1100
Hugh Blemings hugh@blemings.org wrote:
This got me to wondering if a Rubidium based standard might do the trick
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.
As TvB wrote, a single one will not do the trick. You will need
a stability 1e-14 @1d. IIRC most Rb standards floor out at 1e-12 to 1e-13
somewhere between 1k and 100k seconds. Even the Super-5065 has a floor
of about 3-4e-14 (unless our friends here improved on this already).
There will be a few things that you will need to do, if you want to go
with Rubidiums:
- Stabilize or compensate for environmental effects (temperature, air pressure)
- Build ensembles of Rb clocks.
The former is to prevent the ADEV from "turning upwards" again and
keep the Rb's as stable as possible as long as possible. I have no
experience how much this helps, but I suspect, with the correct modeling
that you could get the ADEV to be flat up to a day, maybe even two.
You will have to include aging and drift of the cell itself in the model.
This also means that you will have your Rbs running for a few weeks/months
prior to any measurement so that the aging settles down a bit.
The ensemble is to get the ADEV down. Averaging of clocks with the same
noise decreases the ADEV by the square root of the number of clocks used.
If you are close to the ADEV you need, the averaging will help you getting
it further down. Unfortunately, getting from 1e-13 down to 1e-14 is
impractical as you'd need 100 clocks to average over.... But a factor
of 2 to 3 should be possible.
Alternatively, you can ask Oscilloquartz whether they let you borrow
two of their new OSA3300 for a publicity stunt :-)
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
Get a weather balloon. Or there might already be an amateur group that
launches these. Balloons can go much higher than your local mountains.
You al ill want to build an environmental chamber for the Rb clock. The
chamber is heated and pressurized.
Even for the maintain top experiment you will need data on how the clock
reacts to the pressure and temperatures on the mountain and also along the
way to and from the mountain so you will need a way to simulate this at
home so you can measure the effect. Maybe just as easy to keep the clocks
both in a sea level environment.
On Tue, Mar 21, 2017 at 4:28 AM, Bob Camp kb8tq@n1k.org wrote:
H
On Mar 21, 2017, at 4:58 AM, Tom Van Baak tvb@LeapSecond.com wrote:
Hi Hugh,
If I do the math correctly that's about 14ns difference per 24h the
clocks are separated by that altitude. [1]
That's correct. For your 1500m elevation gain, the gravitational
redshift, the df/f frequency change, will be about 1.6e-13. To be able to
measure with any confidence you'll want your clocks to be stable to about
2e-14, at tau 1 or 2 days.
This got me to wondering if a Rubidium based standard might do the trick
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.
There are tricks and technical factors, but the main one is how stable
these are at tau 1 day. Buy or borrow a few of them and see if they are
mutually stable to the level required. I suspect not. But perhaps other
time nuts could comment on how stable their surplus Rb are out to tau 1 day.
There are lots of other details; some to your advantage, some not. But
if the surplus Rb can't perform down in the -14's at a day, even in
laboratory conditions, then the rest of the discussion doesn't matter.
An ex-telecom Rb will run a bit below 1x10^-12, but not below 1x10^-13 at
tau = 1 day. Roughly speaking it’s about 10X less stable than you need.
That’s in a carefully controlled temperature and pressure environment. One
fake out with Rb’s is that they are pressure sensitive. You will see an
impact simply from the lower pressure on the top of the mountain. How much
impact varies from unit to unit. It’s a good bet you need to compensate for
it well before you get to 1x10^-13 on a mountain trip.
To put this all in context, a 5071 in good condition can (barely) do this
experiment by running up to a mountain top. There’s a lot of fiddly details
you need to take care of even with a 5071. AFIK, Tom is the first to do it
this way (Cs in the back of the family car). All previous work with older
Cs standards had to go to much greater lengths to observe the effect. If
you take a standard up to satellite orbit sort of altitude, you get a shift
of ~1.5x10^-10. That would be fine for a number of frequency standards. It
is not very practical on the transport side of the experiment.
Many options, but none of them easy.
Bob
Yes, the TAPR TICC counter would work well for this experiment. But to
be honest, any old nanosecond-level counter is good enough. I say this not
to discourage you from a good excuse to buy a TICC, but to encourage you to
do the ADEV math to see how clocks and counters and tau can interact in
your favor.
/tvb
----- Original Message -----
From: "Hugh Blemings" hugh@blemings.org
To: "Discussion of precise time and frequency measurement" <
Sent: Monday, March 20, 2017 7:38 PM
Subject: [time-nuts] Time Dilation tinkering
Hi,
I've been mostly lurking on the list for some time now and follow with
interest the many discussions. Very much at the early stages of my
time-nut journey, but enjoying it so far :)
I'd like to have a go at re-creating the efforts of Tom (and I gather
others) in taking a clock up a mountain for a while and seeing if I can
measure the relativistic changes.
Being based in Australia gives me a couple of challenges, for one we
don't really do mountains in the same sense as much of the rest of the
world - so the highest peak I can readily get to from Melbourne is about
1,600m ASL. I live at 80m ASL - so a delta of around 1,500m altitude
and several hundred km drive.
If I do the math correctly that's about 14ns difference per 24h the
clocks are separated by that altitude. [1]
We also lack quite the same surplus market here as the US, so purchasing
a Caesium based standard is well beyond my means.
This got me to wondering if a Rubidium based standard might do the trick
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.
Clearly there'd need to be a bunch of extra gubbins [2] added to the
10MHz standard to turn it into an actual clock/counter including battery
backup and so forth. And would need a pair of everything.
Before I delve too far into the planning, I'd be interested in feedback
as to whether this style of Rb standard is likely to be up to the task
of being the core of such an endeavour or not ?
Oh I should add - my plan was to build the systems such that they
function as nice standalone time/frequency references once this
experiment is concluded :)
Thanks in advance,
Kind Regards/73,
Hugh
VK3YYZ/AD5RV
[1] gh/c^2 x 3600 x 24 Where h is 1500, g and c the usual values :)
[2] I presume at a minimum a counter running at a 5ns or less "tick" fed
from a frequency source locked to the 10MHz of the Rb standard. This
counter would need to be latched for reading from an external signal so
that it can be compared to the second clock. Not sure but seems the
TAPR TICC might have role here :)
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/m
ailman/listinfo/time-nuts
and follow the instructions there.
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To unsubscribe, go to https://www.febo.com/cgi-bin/m
ailman/listinfo/time-nuts
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--
Chris Albertson
Redondo Beach, California
Or perhaps use the Symmetricom CSAC ...
Relatively expensive but might work
On Mar 21, 2017, at 8:08 AM, Attila Kinali attila@kinali.ch wrote:
On Tue, 21 Mar 2017 13:38:51 +1100
Hugh Blemings hugh@blemings.org wrote:
This got me to wondering if a Rubidium based standard might do the trick
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.
As TvB wrote, a single one will not do the trick. You will need
a stability 1e-14 @1d. IIRC most Rb standards floor out at 1e-12 to 1e-13
somewhere between 1k and 100k seconds. Even the Super-5065 has a floor
of about 3-4e-14 (unless our friends here improved on this already).
There will be a few things that you will need to do, if you want to go
with Rubidiums:
- Stabilize or compensate for environmental effects (temperature, air pressure)
- Build ensembles of Rb clocks.
The former is to prevent the ADEV from "turning upwards" again and
keep the Rb's as stable as possible as long as possible. I have no
experience how much this helps, but I suspect, with the correct modeling
that you could get the ADEV to be flat up to a day, maybe even two.
You will have to include aging and drift of the cell itself in the model.
This also means that you will have your Rbs running for a few weeks/months
prior to any measurement so that the aging settles down a bit.
The ensemble is to get the ADEV down. Averaging of clocks with the same
noise decreases the ADEV by the square root of the number of clocks used.
If you are close to the ADEV you need, the averaging will help you getting
it further down. Unfortunately, getting from 1e-13 down to 1e-14 is
impractical as you'd need 100 clocks to average over.... But a factor
of 2 to 3 should be possible.
Alternatively, you can ask Oscilloquartz whether they let you borrow
two of their new OSA3300 for a publicity stunt :-)
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
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.
On 3/21/17 12:51 PM, Scott McGrath wrote:
Or perhaps use the Symmetricom CSAC ...
Relatively expensive but might work
The CSAC is 8E-12 AVAR at 1000 seconds, comparable to a Rb.
See also http://tycho.usno.navy.mil/ptti/2011papers/Paper27.pdf
which shows a bit better performance (3E-12 @ 1000s), but the best
performance appears to be at 10,000 seconds.
but don't you need better?
Attila wrote> You will need a stability 1e-14 @1d.
These are less stable than a rubidium eg tau=10e-11@1000s and monthly
ageing of 9e-10.
The price of these has gone up too- they're now about US5000.
Cheers
Michael
On Wed, 22 Mar 2017 at 7:03 am, Scott McGrath scmcgrath@gmail.com wrote:
Or perhaps use the Symmetricom CSAC ...
Relatively expensive but might work
On Mar 21, 2017, at 8:08 AM, Attila Kinali attila@kinali.ch wrote:
On Tue, 21 Mar 2017 13:38:51 +1100
Hugh Blemings hugh@blemings.org wrote:
This got me to wondering if a Rubidium based standard might do the trick
- the Efratom SLCR-101s seem readily available for ~USD$200 mark.
As TvB wrote, a single one will not do the trick. You will need
a stability 1e-14 @1d. IIRC most Rb standards floor out at 1e-12 to 1e-13
somewhere between 1k and 100k seconds. Even the Super-5065 has a floor
of about 3-4e-14 (unless our friends here improved on this already).
There will be a few things that you will need to do, if you want to go
with Rubidiums:
- Stabilize or compensate for environmental effects (temperature, air
pressure)
- Build ensembles of Rb clocks.
The former is to prevent the ADEV from "turning upwards" again and
keep the Rb's as stable as possible as long as possible. I have no
experience how much this helps, but I suspect, with the correct modeling
that you could get the ADEV to be flat up to a day, maybe even two.
You will have to include aging and drift of the cell itself in the model.
This also means that you will have your Rbs running for a few
weeks/months
prior to any measurement so that the aging settles down a bit.
The ensemble is to get the ADEV down. Averaging of clocks with the same
noise decreases the ADEV by the square root of the number of clocks used.
If you are close to the ADEV you need, the averaging will help you
getting
it further down. Unfortunately, getting from 1e-13 down to 1e-14 is
impractical as you'd need 100 clocks to average over.... But a factor
of 2 to 3 should be possible.
Alternatively, you can ask Oscilloquartz whether they let you borrow
two of their new OSA3300 for a publicity stunt :-)
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
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https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On 3/21/17 1:40 PM, Michael Wouters wrote:
These are less stable than a rubidium eg tau=10e-11@1000s and monthly
ageing of 9e-10.
The price of these has gone up too- they're now about US5000.
Really? That's a big increase. I bought some last year (well, in
December 2015) and they were $1568 ea.
It was a pain to buy them because Microsemi fell off JPL's approved
supplier list.
Michael is correct re pricing
Now significantly higher on CSAC's (see attached justification)
Best regards
Chris Dawes
0409 154 684
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of jimlux
Sent: Wednesday, 22 March 2017 8:25 AM
Subject: Re: [time-nuts] Time Dilation tinkering
On 3/21/17 1:40 PM, Michael Wouters wrote:
These are less stable than a rubidium eg tau=10e-11@1000s and monthly
ageing of 9e-10.
The price of these has gone up too- they're now about US5000.
Really? That's a big increase. I bought some last year (well, in December 2015) and they were $1568 ea.
It was a pain to buy them because Microsemi fell off JPL's approved supplier list.
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.
