Re: [time-nuts] Time Dilation tinkering

[Bob Bownes]

It's not getting one past the airport authorities that's the issue. It's 
getting one that's powered up past them. ;)

Written from about 10,000'. :)

> On Mar 22, 2017, at 20:15, Tom Van Baak  wrote:
> 
> Chris Albertson wrote:
>> Why drive up a mountain?
> 
> "Because it's there" ;-)  And because there's a paved road, and it's free, 
> and there's a place to stay overnight, and the mountain doesn't move. Plus a 
> car makes a good portable time lab; you can share the experience with family 
> or students or visiting time nuts; and a number of technical reasons.
> 
> But most importantly: you can remain at altitude as long as you want -- in 
> order to accumulate just enough nanoseconds of time dilation to meet your 
> experiment's S/N goal -- without running into (or much worse, going beyond) 
> the flicker floor of your clocks.
> 
> There are several different ways to measure time dilation with atomic clocks. 
> Some notes here:
> http://leapsecond.com/pages/atomic-tom/
> 
> 
>> Take the clock with you inside the pressurized cabin of a commercial airliner
> 
> Yes, and this has been done many times. The first (1971) and most famous of 
> all traveling clock relativity experiments is:
> https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment
> 
> For vintage hp flying clock articles see:
> https://www.febo.com/pipermail/time-nuts/2013-January/073743.html
> 
> Two modern examples are described here:
> 
> "Time flies"
> http://www.npl.co.uk/news/time-flies
> 
> "Demonstrating Relativity by Flying Atomic Clocks"
> http://www.npl.co.uk/upload/pdf/metromnia_issue18.pdf
> 
> /tvb
> 
> - Original Message - 
> From: Chris Albertson 
> To: Tom Van Baak ; Discussion of precise time and frequency measurement 
> Sent: Tuesday, March 21, 2017 7:12 PM
> Subject: Re: [time-nuts] Time Dilation tinkering
> 
> "flight" there is the word.Why drive up a mountain?   Take the clock with 
> you inside the pressurized cabin of a commercial airliner next time you are 
> on one of those 10 hour trans=pacific flights.   You be taller then any 
> mountain and it is actually cheaper then a weather balloon. 
> 
> Can you get a Rb clock past the TSA x-ray machine.   Maybe if you ask first.  
> There must be a way to hand cary specialized equipment.
> 
> On Tue, Mar 21, 2017 at 7:03 PM, Tom Van Baak  wrote:
> 
> But attached is one of the first plots where I put a SA.32m in a home-brew 
> vacuum chamber and pulled down to a few inches of Hg for a few hours to 
> simulate the low pressure of a flight up to 50 or 90,000 ft. For a high 
> altitude relativity experiment -- where you'd like your clock to remain 
> stable to parts in e-13 and not accumulate too many stray ns -- it's not a 
> good sign when your clock changes by 2e-11 (that's more than 1 ns per minute) 
> just because of ambient pressure changes.
> 
> 
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Re: [time-nuts] PLL performance?

[David Scott Coburn]

I will not be using an off-the-shelf optical interrupter  type sensor for this.

I have designed a custom IR LED -> IR photodiode unit which will have a flag 
that blocks half of the IR signal when the pendulum is stopped, and the motion 
of the pendulum will modulate this 50% signal from about 25% to 75%.  The 
output will be an analog 'sine' wave.  This sine wave goes into some custom 
analog electronics which separates the DC and AC parts of the signal, does some 
amplification, and then into a precision zero-crossing detector (ZCD) circuit.  
I have assembled these circuits and have been testing them at zero DC (ie, no 
DC offset or sine input).  The next step is to connect the LED/photodiode 
circuit and characterize the circuit with just the DC signal (as it would be if 
the pendulum was not moving).  This stage of the testing is looking for noise 
and long-term stability issues.  I have not yet injected a reference sine 
signal to characterize the circuit's AC performance.  On my todo list!  :)

I hoped to characterize the jitter of the ZCD circuit with a good low-jitter 
reference AC signal as an input, but it is not trivial to generate such a 
signal!  (Short of spending lots of $$$ on a *good* signal generator.)  I have 
an HP3325A which I intend to use for this but the 0.5 Hz output has quite a lot 
of jitter (not unexpected considering the way it is generated).  But, I guess 
this is not so much of an issue, since I just need to see if the ZCD circuit 
makes the jitter worse.

The PLL circuit will not be used to characterize the performance of the 
pendulum, it will just be used to drive the display.  The output of the ZCD 
circuit will be fed directly into a 'time-stamp counter' circuit to monitor the 
pendulum performance.  To some degree it will be good to have a nice low-jitter 
signal from the pendulum, but I am more interested in the longer-term 
performance , where the jitter (hopefully!) is all averaged out.

(The DC part of the signal will be monitored for changes in the LED output (to 
monitor its stability) and there is a precision rectifier circuit to monitor 
the amplitude of the AC part of the signal (which is proportional to the 
amplitude of the pendulum motion).  And, there is a precision voltage reference 
for driving all of these circuits.)

Cheers,

Scott

(Maybe this answer was more than you bargained for!)

On Wednesday, March 22, 2017 12:19:09 PM EDT Scott Stobbe wrote:
> Neat Project. I don't know if it will come up for you but optical or hall
> rotary encoders are notorious for jitter. While a generic IC comparator may
> have an open loop-gain of 100 dB, creating the mechanical equivalent is not
> so easy. Hall/optical have a softer switch on/off curve. Depending what you
> choose to instrument your pendulum may also introduce more jitter. The
> 20logN dosen't help either, 1 millideg at 0.5 Hz is 5.5 cycles at 1 MHz.
> 
> On Mon, Mar 20, 2017 at 9:07 PM, David Scott Coburn 
> 
> wrote:
> > Hi All,
> > 
> > I have built and tested a PLL circuit that will be used to generate a 1
> > MHz signal locked to a 0.5 HZ signal from a pendulum.  (Details available
> > upon request.)



> > Cheers,
> > 
> > Scott
> > ___
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Re: [time-nuts] Time Dilation tinkering

[MLewis]

On 22/03/2017 10:56 AM, jimlux wrote:

On 3/22/17 4:04 AM, Angus wrote:

No tall mountains in Australia, but...

Pikes Peak in the US is 14114 ft, 4304m and has a road to the top. Of 
course the base is at about 5000 ft/1600 m


In EU, there's probably a Seilbahn of some sort pretty high up in the 
Alps, although probably not to 4000m.




I've driven a few passes in Colorado above 10,000 and one above 12,000.
Four are above 12,000 ft, highest at 3,712 metres (12,183 ft).
https://en.wikipedia.org/wiki/List_of_mountain_passes_in_Colorado
Nine of those are higher than the top of the Eiger.

http://www.dangerousroads.org/rankings23/1610-highest-paved-road-list-in-usa.html

If it's the difference in height in a day, one option in Switzerland is 
the cog train to the Jungfraujoch. That's 3,466 metres (11,371 ft). The 
Jungfraubahn is listed as 3,454 metres (11,332 ft). It's not cheap; with 
my ski pass, I never went beyond the Eigergletscher.
You could start from Grindelwald at 1,034 m (3,392 ft) or from 
Lauterbrunnen at 802 m (2,631 ft).
You can drive to either from Interlaken, and there used to be a train, 
so you could start from 566 m (1,857 ft).


Michael
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Re: [time-nuts] Time Dilation tinkering

[Tom Van Baak]

Chris Albertson wrote:
> Why drive up a mountain?

"Because it's there" ;-)  And because there's a paved road, and it's free, and 
there's a place to stay overnight, and the mountain doesn't move. Plus a car 
makes a good portable time lab; you can share the experience with family or 
students or visiting time nuts; and a number of technical reasons.

But most importantly: you can remain at altitude as long as you want -- in 
order to accumulate just enough nanoseconds of time dilation to meet your 
experiment's S/N goal -- without running into (or much worse, going beyond) the 
flicker floor of your clocks.

There are several different ways to measure time dilation with atomic clocks. 
Some notes here:
http://leapsecond.com/pages/atomic-tom/


> Take the clock with you inside the pressurized cabin of a commercial airliner

Yes, and this has been done many times. The first (1971) and most famous of all 
traveling clock relativity experiments is:
https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment

For vintage hp flying clock articles see:
https://www.febo.com/pipermail/time-nuts/2013-January/073743.html

Two modern examples are described here:

"Time flies"
http://www.npl.co.uk/news/time-flies

"Demonstrating Relativity by Flying Atomic Clocks"
http://www.npl.co.uk/upload/pdf/metromnia_issue18.pdf

/tvb

- Original Message - 
From: Chris Albertson 
To: Tom Van Baak ; Discussion of precise time and frequency measurement 
Sent: Tuesday, March 21, 2017 7:12 PM
Subject: Re: [time-nuts] Time Dilation tinkering

"flight" there is the word.Why drive up a mountain?   Take the clock with 
you inside the pressurized cabin of a commercial airliner next time you are on 
one of those 10 hour trans=pacific flights.   You be taller then any mountain 
and it is actually cheaper then a weather balloon. 

Can you get a Rb clock past the TSA x-ray machine.   Maybe if you ask first.  
There must be a way to hand cary specialized equipment.

On Tue, Mar 21, 2017 at 7:03 PM, Tom Van Baak  wrote:

But attached is one of the first plots where I put a SA.32m in a home-brew 
vacuum chamber and pulled down to a few inches of Hg for a few hours to 
simulate the low pressure of a flight up to 50 or 90,000 ft. For a high 
altitude relativity experiment -- where you'd like your clock to remain stable 
to parts in e-13 and not accumulate too many stray ns -- it's not a good sign 
when your clock changes by 2e-11 (that's more than 1 ns per minute) just 
because of ambient pressure changes.


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Re: [time-nuts] Time Dilation tinkering

[Trent Piepho]

On Wed, Mar 22, 2017 at 9:39 AM, David C. Partridge
 wrote:
> Aiguille du Midi is 3842m IIRC (cable car base station at about 1000m).
>
> Dave
>
>
> Pikes Peak in the US is 14114 ft, 4304m and has a road to the top. Of course 
> the base is at about 5000 ft/1600 m
>
> In EU, there's probably a Seilbahn of some sort pretty high up in the Alps, 
> although probably not to 4000m.

Mauna Kea in Hawaii lets one drive from sea level to 13,796 ft, 4204
m.  Pretty big delta for a few hours of over land travel.
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Re: [time-nuts] Time Dilation tinkering

[Magnus Danielson]

Hi,

On 03/22/2017 05:55 PM, Attila Kinali wrote:

On Wed, 22 Mar 2017 07:56:45 -0700
jimlux  wrote:


In EU, there's probably a Seilbahn of some sort pretty high up in the
Alps, although probably not to 4000m.


But almost: https://en.wikipedia.org/wiki/Klein_Matterhorn
You could start in Sion(500m) or Visp(660m) take the train to Zermatt(1600m)
and from there the cablecar up to Klein Matterhorn(3880m). That would
give a nice 3000m of height difference. From Sion it takes 2.5h to 3h,
from Visp 2h to 2.5h. So you could potentially get up in the morning,
go up, install everything and be back for dinner :-)

If anyone wants to do that, please let me know. :-)


We both where uhm. kind of "volunteered" for a similar mission.
I would not mind a little "vacation" like that.

Cheers,
Magnus
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Re: [time-nuts] Time Dilation tinkering

[Bob kb8tq]

Hi

The outer can is at best only “sort of” sealed. 

Bob
> On Mar 22, 2017, at 10:58 AM, jimlux  wrote:
> 
> On 3/22/17 4:28 AM, Bob Camp wrote:
>> Hi
>> 
>> In this case, the vacuum might work against you. You change the pressure 
>> outside
>> the package and you get a flex. Flex translates to dimensional changes. That 
>> gives you
>> a frequency shift. People make absolute pressure sensors this way :) Rb’s 
>> are by no
>> means the only frequency standard impacted by this effect. Precision OCXO’s 
>> have the
>> same issue.
>> 
>> If you had enough room inside the package, you could do a “can in a can” 
>> sort of approach.
>> The outer vacuum sealed can flexes. The inner vacuum sealed can does not see 
>> anything.
>> You don’t eliminate the sensitivity this way, you do attenuate it quite a 
>> bit with each layer.
>> The question then becomes - is is worth the increase in size? Since the 
>> pressure sensitivity
>> is well below many other environmental factors …. probably not.
>> 
> 
> The CSAC is a can within a can (or more properly, the physics package is 
> inside a sealed can) but I don't know if there's vacuum inside the can.
> 
> 
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Re: [time-nuts] Time Dilation tinkering

[Majdi S. Abbas]

On Wed, Mar 22, 2017 at 07:52:38AM -0700, jimlux wrote:
> I imagine there's a "de minimis" quantity.  We didn't declare the cesium in
> the CSAC that we hand carried, and I'm pretty sure people have hand carried
> SRS Rb sources.

The letter they have covers anything up to a gram of Rb.
Certainly I'm not worried about it, I hand carry all sorts of things on
planes.

> off of the MSDS from Symmetricom/Microsemi
> 
> "All Symmetricom’s rubidium product can be shipped both domestically and
> internationally as a non-hazardous product. Symmetricom has received letters
> of interpretation from both the United States Department of Transportation
> (US DOT)Ref. No. 08-0154 and the International Air Transport
> Association(IATA) stating that Symmetricom’s rubidium product are not
> considered a hazardous Class 4 material in transportation.

2008 letter and response here:


https://www.phmsa.dot.gov/staticfiles/PHMSA/DownloadableFiles/Files/Interpretation%20Files/2008/080154.pdf

--msa
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Re: [time-nuts] Antique precision timing device without

[Brooke Clarke]

Hi Morris:

The GR 631 StroboTac includes a power line driven vibrating reed sticking into the reflector and so it's motion is 
stopped by the strobe.

The patent has hand written comments regarding that idea.
http://www.prc68.com/I/GRstrobotac.html#2331317
http://www.prc68.com/I/Images/Strobotac631-01b.jpg

The idea here was to use the power line as a frequency reference.
This would be fine since most of the applications for this strobe were related 
to line driven motors.

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

 Original Message 

HI all,

Thanks to all those who responded to my post and also for the great pics of
other tuning forks. It's amazing that they were still being used for
electronic purposes as recently as the 1960s. Actually now that I think
about it I have seen little tuning forks used to check the function of
modern police speed radars so they still have some use. Musicians don't use
them any more - guitar players will know the little electronic tuning
devices clipped to the  neck of the instrument that displays the frequency
or key of each string. Doctors still use 125 Hz forks to test vibration
sense and higher frequency ones to test for conductive hearing loss.

In answer to some of the questions posted: no there was no documentation
with the unit. The most useful thing was the "12 volts in" label on the
power socket so I knew where to start. The rest of it was necktop analysis.
The fork is maintained by means of a central electromagnet and small leaf
spring contacts on the tines - they also provide the 25 Hz power for the
motor which runs at 12 volts. Of course they would reduce the Q of the fork
a little and affect its resonance but I'm sure that was taken into  account
by the designer and the frequency & symmetry can be adjusted with the
weights on the ends. Operating current is about 0.5A at 12 volts when
running and 1A when the fork is not vibrating. There's a switch marked "Neon
Lamp" that controls the AC supply to a pair of clips between the tines of
the fork. They are about 3-4 inches apart and I have no idea what sort of
long thin tubular lamp would fit between them. Just for fun I'm going to
make a simple stroboscope with a 555 timer and some high intensity white
LEDs I have lying around to see if I can use it on the fork.

Cheers,

Morris

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Re: [time-nuts] WTB: GPSDO

[Chris Caudle]

On Wed, March 22, 2017 3:52 pm, Nick Sayer via time-nuts wrote:
> My thunderbolt *insists* on being on the DC Pass port. If you put it on a
> DC Block port (yes, something *else* is on the DC pass port and supplying
> DC for the antenna and splitter at the time - other connected devices work
> just fine) it's deaf.

You need a DC load so that the GPS receiver thinks there is an active
antenna attached. I think that is just a quirk of the Thunderbolts, that
rather than just flagging an alarm and continuing to run, it gives up and
won't even try to run.
-- 
Chris Caudle




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Re: [time-nuts] PLL Digital Loop Filter

[Bob kb8tq]

Hi


> On Mar 22, 2017, at 7:50 AM, Attila Kinali  wrote:
> 
> On Tue, 21 Mar 2017 21:45:24 -0400
> Bob Camp  wrote:
> 
>> 1) You need a way to digitize the phase input with adequate resolution. If 
>> you have a 1 second period and want 1 ns, you need a way to digitize at
>> a 1:1,000,000,000 sort of level. That’s in the 30 bit range so a simple
>> ADC isn’t going to do it alone. 
> 
> That depends on how the phase difference is measured. If the whole
> measurement period needs to be encoded, then yes, the number of
> bits needed will make it difficult. But usually the input frequency
> range is limited, which allows to measure and encode just the difference
> between expected and actual arrival time of the pulse/edge. The integrated
> version of these PLLs (the ADPLL - all digitall PLL), if they have a
> real TDC, have only a resolution in the order of 7-8 bits (IIRC I've seen
> down to 4 bits). And then there is the class of those Bang-Bang PLL,
> which only encode one bit: early/late. Eventhough they are relatively
> crude and rely on the loopfilter to smooth things out, they perform
> quite well. 

We started out with an XOR that has a 50/50 duty cycle. An early /late
process only works if you run the outputs through an ADC and calibrate 
them to some degree. Then you are right back to a lot of resolution time wise.

Bob

> 
>   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
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Re: [time-nuts] PLL performance?

[Bob kb8tq]

Hi

As others have pointed out, a control loop at 100 seconds is more a gain spec 
than 
an R/C time constant spec. The real issue is that you should have an integrator 
on 
the loop and that *is* an R/C sort of thing. It’s also likely to have a much 
longer time
constant than the magic number for the loop. 

Bob

> On Mar 22, 2017, at 2:24 PM, Hal Murray  wrote:
> 
> 
> att...@kinali.ch said:
>> There have been a couple of discussions about doing GPSDOs using only analog
>> components in the past. People fare more knowledgable than me have commented
>> there on what the challenges would be and how to solve them. So I recommend
>> to go through the archives and look for those discussions. They might be a
>> little bit hidden, though. 
> 
> I think the main problem is how to build a filter with a time constant of 
> many seconds.  The better your OCXO the longer the time span you can 
> integrate over.  100s of seconds isn't an unreasonable target.
> 
> There may be other problems.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Fwd: Fwd: HP5061B Ion Current

[John Miles]

Yeah, I wouldn't worry about the oven, but the ionizer filament is a different 
story.  Those can definitely open up.

-- john,  KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of
> Donald E. Pauly
> Sent: Wednesday, March 22, 2017 11:32 AM
> To: time-nuts; rwa...@aol.com; Donald E. Pauly
> Subject: [time-nuts] Fwd: Fwd: HP5061B Ion Current
> 
> https://www.febo.com/pipermail/time-nuts/2017-March/104374.html
> 
> I have posted two HP patents on the cesium beam tube at
> http://gonascent.com/papers/hp/US3323008.pdf and
> http://gonascent.com/papers/hp/US3397310.pdf . Both are of academic
> interest. The first claims that the cesium oven operates at 60°-70° C.
> This is a tiny heating compared to a 1,000° filament on a power
> transmitting tube.  I say that it can be cycled a million times with
> no problem of thermal cracking.
> 
> πθ°μΩω±√·Γλ
> WB0KVV
> 

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Re: [time-nuts] Time Dilation tinkering

[Richard (Rick) Karlquist]

On 3/21/2017 7:12 PM, Chris Albertson wrote:

"flight" there is the word.Why drive up a mountain?   Take the clock
with you inside the pressurized cabin of a commercial airliner next time
you are on one of those 10 hour trans=pacific flights.   You be taller then
any mountain and it is actually cheaper then a weather balloon.


Yes Len Cutler did that 50 years ago, but the velocity of the plane also
has relativistic effects, so it's not a pure play.

Rick
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Re: [time-nuts] Time Dilation tinkering

[jimlux]

On 3/22/17 10:07 AM, Arnold Tibus wrote:



No tall mountains in Australia, but...

Pikes Peak in the US is 14114 ft, 4304m and has a road to the top. Of
course the base is at about 5000 ft/1600 m

In EU, there's probably a Seilbahn of some sort pretty high up in the
Alps, although probably not to 4000m.


I like the englisch word 'Seilbahn' ;-)
Well, the equipment is all made by German speaking companies, even in 
the US, so it seems an appropriate term.  Cable Car or Gondola aren't a 
unique description (i.e. Cable Cars in San Francisco and Gondolas in Venice)




Yes, not fully up to 4000 m, but there are in fact quite close to the
possibilities I know:

1. Klein Matterhorn, Walliser Alpen, Schweiz
Bergstation: 3820 m,

2. Aiguille du Midi, France
Télépherique de l’Aiguille du Midi
from Chamonix
Bergstation: 3777 m
Gourmet-Restaurant, 3842 m



Now that I think about it, though, speed of transit isn't as important 
as "length of time at altitude", because if we're following tvb's GREAT 
experiment, you have some clocks you leave at the low elevation, then 
some clocks you take high for while, then bring back low, and you 
compare the apparent "elapsed time". So longer duration helps increase 
the delta (but also, of course, adding to the variance of the two 
measurements, so there's a tradeoff).


So, are you better off with a week long camping trip at a moderate 
altitude, or a 14 hour flight at 10-15,000 meters.  Or would you take a 
small battery powered package up to the Bergstation and leave it there 
for a week?


The airport in La Paz, Bolivia is at around 4000 meters, the city itself 
at 3600m.



With relatively inexpensive atomic clocks, could one, with clever 
mailing addresses, send two clocks the opposite directions around the 
earth, and duplicate the famous traveling clocks experiment.  For 
instance, with a collaborator in Australia or India, EU, and US, you 
could probably arrange for the packages to go the "correct" direction.


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Re: [time-nuts] Time Dilation tinkering

[Magnus Danielson]

Hi,

On 03/22/2017 12:02 AM, Tom Van Baak wrote:

Scott McGrath wrote:

Or perhaps use the Symmetricom CSAC ...


Chris Albertson wrote:

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'll both be interested to hear that CSAC+balloon was proposed for the "Genius by 
Stephen Hawking" TV program and, yes, we were in touch with amateur high altitude 
balloon groups. The producer rightly thought that a small atomic clock going up in a 
helium balloon would make dramatic video for a time dilation demonstration. Symmetricom / 
Microsemi donated a SA.* series clock to the effort.

I got involved on the science and engineering side of the equation. Spent a month 
trying to make it work and in the end the balloon idea was dropped. Just too hard, 
and too uncertain, and would require many more months of R, and finger 
crossing. So that's why, instead, I drove six calibrated 5071A down to Tucson for a 
conventional mountain-valley time dilation experiment -- which I knew from prior 
experience would work, especially with 3x redundancy. 
http://leapsecond.com/great2016a/

Note that miniature Rb and Cs clocks (such as those sold by Microsemi) are very 
small, ultra light, and amazingly low power -- but their long-term stability 
(including environmental effects) is a hundred or even a thousand times worse 
than a 5071A/001. This is not to say CSAC are poor clocks. In fact they have a 
superb mass/power/size to adev ratio, and thus there are many unique 
applications for them. But they are not designed to be laboratory-quality 
frequency standards


Indeed. CSAC is a superb clock for the power it consumes, and that is 
the market segment it attempts to address. For the same size and more 
power, you get much better stability. Just because it has Cesium doesn't 
make it a laboratory clock, it's a small gas-cell, with all the issues 
of one.


Which reminds me, I got three CSACs to measure. Into the lab I go.

Cheers,
Magnus
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Re: [time-nuts] WTB: GPSDO

[Nick Sayer via time-nuts]

> On Mar 22, 2017, at 12:40 AM, Thomas Petig  wrote:
> 
> 
> The special GNSS splitters forward DC only from one port and provide
> some 200 Ohm DC termination together with the DC-block on the other
> ports to keep the receiver happy, i.e., it seems current consumption and
> therefore believes the antenna is ok. Some have an amplifier to
> compensate for the loss of the splitter, but it is not necessary if the
> antenna delivers enough.
> 

Just a little side query… For those using one of these sorts of splitters with 
a Thunderbolt, have you seen anything odd?

My thunderbolt *insists* on being on the DC Pass port. If you put it on a DC 
Block port (yes, something *else* is on the DC pass port and supplying DC for 
the antenna and splitter at the time - other connected devices work just fine) 
it’s deaf. I’ve worked around it by giving the pass port to the TBolt and 
running everything else on a block port, so it’s not a deal-breaker or 
anything, but it’s a bit awkward and otherwise unexplainable. 
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[time-nuts] Fwd: Fwd: HP5061B Ion Current

[Donald E. Pauly]

https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

I have posted two HP patents on the cesium beam tube at
http://gonascent.com/papers/hp/US3323008.pdf and
http://gonascent.com/papers/hp/US3397310.pdf . Both are of academic
interest. The first claims that the cesium oven operates at 60°-70° C.
This is a tiny heating compared to a 1,000° filament on a power
transmitting tube.  I say that it can be cycled a million times with
no problem of thermal cracking.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: John Miles 
Date: Tue, Mar 21, 2017 at 5:41 PM
Subject: Re: [time-nuts] Fwd:  HP5061B Ion Current
To: Discussion of precise time and frequency measurement
, rwa...@aol.com

That's some very nice work, Donald.  Looking back, I have junked one
or two Cs tubes that might have been usable if I'd thought through the
problem of high ion pump current as you and KB7APQ seem to have done.

Another good reason to raise the lockout threshold would be to cut
down on the repetitive ionizer filament cycling that the tube will
otherwise undergo when you first fire up the oven.  That phenomenon
always makes me rally nervous.

-- john, KE5FX
Miles Design LLC

> -snip-
> When we overrode the cesium lockout at 29 μA or so of ion current, we
> needed only minor front panel adjustments for beam current of 20 μA.
> (We shorted across A15 R-4.) Our last ion current before power supply
> modifications at risen to 39 uA.  Beam current has been stable.
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Re: [time-nuts] PLL performance?

[Hal Murray]

att...@kinali.ch said:
> There have been a couple of discussions about doing GPSDOs using only analog
> components in the past. People fare more knowledgable than me have commented
> there on what the challenges would be and how to solve them. So I recommend
> to go through the archives and look for those discussions. They might be a
> little bit hidden, though. 

I think the main problem is how to build a filter with a time constant of 
many seconds.  The better your OCXO the longer the time span you can 
integrate over.  100s of seconds isn't an unreasonable target.

There may be other problems.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Four hour cycle in GPS NMEA jitter

[Kiwi Geoff]

On 3/22/17, Trent wrote:
> https://goo.gl/photos/JZhBbFKFzkBAykti6
> Why would a GPS module produce jitter with a pattern like this?

Trent, I decided to R.T.F.M.(read the fantastic manual ;-)

It looks like that in your Telit module, there is a mode called

---
Client Generated Extended Ephemeris (CGEE)

CGEE data is always generated for a prediction interval of three days:
- Consists of 18 blocks of 4-hour EE data blocks
- Updated when a newly visible satellite is acquired
- Updated when new broadcast ephemeris is received from a tracked
satellite and the current
EE data block is nearing expiration
- On average, it takes 1.2 seconds per satellite for the receiver to
calculate CGEE
---

So I think that is the cause of your 4 Hour NMEA latency issues, when
your Telit module is  creating a new EE (Extended Ephemeris) data set.

>From a quick glance at the manual, it looks like this mode can be
turned off with:

AT$GPSIFIX=0

That "should" remove your 4 hour NMEA latency issues (fingers crossed).

Regards, Geoff  ( Christchurch , New Zealand )
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Re: [time-nuts] Time Dilation tinkering

[Arnold Tibus]

Am 22.03.2017 um 15:56 schrieb jimlux:
> On 3/22/17 4:04 AM, Angus wrote:
>> On Tue, 21 Mar 2017 13:08:56 +0100, you wrote:
>>
>>> On Tue, 21 Mar 2017 13:38:51 +1100
>>> Hugh Blemings  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:
>>> 1) Stabilize or compensate for environmental effects (temperature,
>>> air pressure)
>>> 2) Build ensembles of Rb clocks.
>>>
>>
>> Hi,
>>
>> Looking back at an old plot I did of a temperature controlled and air
>> pressure compensated LPRO against an M12+T, the Hadamard Deviation of
>> the 1000s averages of the 1PPS measurement was about 5E-14 at 1 day.
>> A large part of that was likely the GPS, so with a better rubidium
>> like an FRK-H in a sealed and temperature controlled enclosure you
>> might be around 1E-14 at 1 day.
>>
>> The bit that I'm not so sure about is the travelling. A long period of
>> movement, vibration, magnetic  fields, etc. all adding in could
>> obscure the effects of time dilation.
>>
>> It might be quite possible, although a nearby mountain and a friend
>> with a helicopter would make it a lot easier!
>>
>
> No tall mountains in Australia, but...
>
> Pikes Peak in the US is 14114 ft, 4304m and has a road to the top. Of
> course the base is at about 5000 ft/1600 m
>
> In EU, there's probably a Seilbahn of some sort pretty high up in the
> Alps, although probably not to 4000m.

I like the englisch word 'Seilbahn' ;-)

Yes, not fully up to 4000 m, but there are in fact quite close to the
possibilities I know:

1. Klein Matterhorn, Walliser Alpen, Schweiz
Bergstation: 3820 m,

2. Aiguille du Midi, France
Télépherique de l’Aiguille du Midi
from Chamonix
Bergstation: 3777 m
Gourmet-Restaurant, 3842 m

Enjoy, good luck!

Arnold
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Re: [time-nuts] Time Dilation tinkering

[David C. Partridge]

Aiguille du Midi is 3842m IIRC (cable car base station at about 1000m).

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of jimlux
Sent: 22 March 2017 14:57
To: time-nuts@febo.com
Subject: Re: [time-nuts] Time Dilation tinkering

On 3/22/17 4:04 AM, Angus wrote:
> On Tue, 21 Mar 2017 13:08:56 +0100, you wrote:
>
>> On Tue, 21 Mar 2017 13:38:51 +1100
>> Hugh Blemings  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:
>> 1) Stabilize or compensate for environmental effects (temperature, 
>> air pressure)
>> 2) Build ensembles of Rb clocks.
>>
>
> Hi,
>
> Looking back at an old plot I did of a temperature controlled and air 
> pressure compensated LPRO against an M12+T, the Hadamard Deviation of 
> the 1000s averages of the 1PPS measurement was about 5E-14 at 1 day.
> A large part of that was likely the GPS, so with a better rubidium 
> like an FRK-H in a sealed and temperature controlled enclosure you 
> might be around 1E-14 at 1 day.
>
> The bit that I'm not so sure about is the travelling. A long period of 
> movement, vibration, magnetic  fields, etc. all adding in could 
> obscure the effects of time dilation.
>
> It might be quite possible, although a nearby mountain and a friend 
> with a helicopter would make it a lot easier!
>

No tall mountains in Australia, but...

Pikes Peak in the US is 14114 ft, 4304m and has a road to the top. Of course 
the base is at about 5000 ft/1600 m

In EU, there's probably a Seilbahn of some sort pretty high up in the Alps, 
although probably not to 4000m.



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Re: [time-nuts] Time Dilation tinkering

[Attila Kinali]

On Wed, 22 Mar 2017 07:56:45 -0700
jimlux  wrote:

> In EU, there's probably a Seilbahn of some sort pretty high up in the 
> Alps, although probably not to 4000m.

But almost: https://en.wikipedia.org/wiki/Klein_Matterhorn
You could start in Sion(500m) or Visp(660m) take the train to Zermatt(1600m)
and from there the cablecar up to Klein Matterhorn(3880m). That would
give a nice 3000m of height difference. From Sion it takes 2.5h to 3h,
from Visp 2h to 2.5h. So you could potentially get up in the morning,
go up, install everything and be back for dinner :-)

If anyone wants to do that, please let me know. :-)

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
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Re: [time-nuts] Time Dilation tinkering

[jimlux]

On 3/22/17 4:28 AM, Bob Camp wrote:

Hi

In this case, the vacuum might work against you. You change the pressure outside
the package and you get a flex. Flex translates to dimensional changes. That 
gives you
a frequency shift. People make absolute pressure sensors this way :) Rb’s are 
by no
means the only frequency standard impacted by this effect. Precision OCXO’s 
have the
same issue.

If you had enough room inside the package, you could do a “can in a can” sort 
of approach.
The outer vacuum sealed can flexes. The inner vacuum sealed can does not see 
anything.
You don’t eliminate the sensitivity this way, you do attenuate it quite a bit 
with each layer.
The question then becomes - is is worth the increase in size? Since the 
pressure sensitivity
is well below many other environmental factors …. probably not.



The CSAC is a can within a can (or more properly, the physics package is 
inside a sealed can) but I don't know if there's vacuum inside the can.



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[time-nuts] Four hour cycle in GPS NMEA jitter

[Mark Sims]

I did a lot of work in Lady Heather to add timing message arrival time analysis 
capability.  Heather has a "set the system clock to receiver time" function 
that is intended to be used on systems without access to something like NTP.  
By knowing the arrival time of the last byte of the timing message, Heather can 
set the system clock more accurately.  You can specify the message arrival time 
offset of the message time code or Heather uses a pre-computed typical value 
for the receiver.

Heather has a mode that can analyze and calculate the message timing offset for 
any receiver / cpu combination.  During the analysis it plots the message 
arrival time offset in milliseconds,  the jitter in the message arrival time,  
and ADEV/HDEV/MDEV and TDEV of those values.  When you exit message analysis 
mode it analyzes a histogram of the arrival time data to calculate an "optimum" 
arrival time offset to use for the system + receiver.

Most timing receivers that can operate in binary mode have rather consistent 
arrival times.  Some NMEA receivers can be quite good and others are rather 
problematic.  Some receivers have rather consistent time for long periods and 
then jump to a new "stable" value.  Also,  doing other things on the system 
during the analysis can cause spikes in the data.

Attached is a table of the arrival time offsets and standard deviations of 
several receivers.



Here are the results of measuring the difference between the time code in 
a GPS receiver time message and the arrival time of the last byte of 
the message.  POSITIVE values mean that the receiver sends the timing 
message AFTER the 1PPS pulse that it describes. The table also shows the 
standard deviation of the message arrival times.



The test configuration was a Compaq N610C laptop (2 GHz Pentium, hardware 
serial port) running Linux Ubuntu Mate 15.10).  The time of the message
arrival was from the system clock synced to NTP.  The receivers were tested 
in native binary protocol and, if supported, NMEA.  The com port was running
at the default value for the receiver.  If not specified that was 9600:8:N:1
Data was collected after the receiver had been tracking satellites for at 
least 1 hour and averaged over 4 hours.  The timings were also checked and
agree with those on a Raspberry PI 3 and a quad-core 3 GHz box.



Although measuring the arrival time of the first byte of the timing message
makes more technical sense (less variation due to timing message length and 
baud rate) these measurements are of the last byte of the message.  This was 
chosen to assist people trying to sync a clock to a GPS receiver without 
relying on the 1PPS pulse.  They are also useful to people that want to know
how long they have to process a timing message (like to set a sawtooth 
compensation delay line) before the next 1PPS pulse comes out.



A few receivers appear to not fully sync their timing message to some reference
clock.  This causes the timing message arrival time to follow a ramp curve.
The ramp size is fairly small in most receivers.



Device Protocol Firmware  (msg-arrival)  sdev

 (msecs)

=    =   =

Thunderbolt TSIPApp:3.0 GPS:10.243.7 *6.2   (gold 
box)

Thunderbolt TSIPApp:2.22 GPS:10.2   54.6 *   10.2   (red 
box)

Resolution-TTSIPGPS:1.2699.4 *5.4

Res-T SMT   TSIPGPS 2.7393.2 *   63.7

Res-T SMT   Motorola(12ch)  HW 3010 SW:0.03.0  519.7 *   49.1

Starloc II  TSIPApp:1.10 GPS:1.2   266.0 *7.2

Nortel NTBW50AA TSIPGPS 10.460.8 *1.2   (made 
by Trimble)

Nortel NTGS50AA TSIPGPS 10.550.8 *2.4   (made 
by Trimble) 

Nortel NTPB15AA TSIPGPS 10.162.8 *1.4   (made 
by Trimble) 

Nortel NTPX26AB TSIPGPS 10.159.8 *1.4   (made 
by Trimble, aka Nortel GSPR) 



NVS NC08C-CSM   BINR 115.2K CSM24 04.08 20/10/1440.7 *7.3



Ublox LEA-6Tbinary  6.02 (36023)   206.0 *4.4

Ublox LEA-6TNMEA6.02 (36023)   144.5 *   11.1

Ublox Neo6M binary  7.03 (45969)   197.1 *9.3

Ublox Neo6M NMEA7.03 (45969)   137.6 *8.4

Ublox 7 binary  1.00 (59842)   178.4 *2.6

Ublox 7 NMEA1.00 (59842)   146.2 *7.9

Ublox NEO-8Mbinary  2.01 (75350)   207.7 *9.1

Ublox NEO-8MNMEA2.01 (75250)   181.2 *8.0


V.KEL SIRFIII   binary  GSW3.2.5   417.0 *6.1

V.KEL SIRFIII   NMEAGSW3.2.5   385.0 *5.0


Navspark Mini   bin+NMEA 115.2K 1.7.27 15.8.18 170.8 *7.1

Navspark NS-T   

Re: [time-nuts] PLL performance?

[Scott Stobbe]

Neat Project. I don't know if it will come up for you but optical or hall
rotary encoders are notorious for jitter. While a generic IC comparator may
have an open loop-gain of 100 dB, creating the mechanical equivalent is not
so easy. Hall/optical have a softer switch on/off curve. Depending what you
choose to instrument your pendulum may also introduce more jitter. The
20logN dosen't help either, 1 millideg at 0.5 Hz is 5.5 cycles at 1 MHz.

On Mon, Mar 20, 2017 at 9:07 PM, David Scott Coburn 
wrote:

> Hi All,
>
> I have built and tested a PLL circuit that will be used to generate a 1
> MHz signal locked to a 0.5 HZ signal from a pendulum.  (Details available
> upon request.)
>
> The circuit is a classic 4046 generating the 1 MHz signal which is fed
> into a 2e6 digital divider which outputs 0.5 Hz which is fed back to the
> 4046 phase comparator (PC).
>
> I take a 1 MHz signal from an HP 107A run through another 2e6 divider to
> generate a reference 0.5 Hz signal for the other 4046 PC input.
>
> I tested this by feeding the 0.5 Hz output of the PLL into a "time-stamp
> counter" board which I built to go into an HP 3582A Data Acquisition unit.
> The TSC uses the 5 MHz signal from the HP 107A to feed a free-running
> 32-bit binary counter.  The 0.5 Hz input latches the count value (on the
> rising edge of the signal), which is then logged.
>
> See the attached diagram.  The PLL under test is in the red box.  (Not
> sure what the policy is here for attachments?)
>
> If all was perfect I would get a string of values of 10,000,000 counts
> each, one every 2 seconds.
>
> Over the course of one day the average reading is, in fact, 10e6, so the
> PLL looks to be working over "long" time scales.
>
> The attached histogram plot shows the actual data for the 0.5 Hz signal,
> showing the distribution of deviations from 10e6 counts.  This is almost a
> full day of data, about 40,000 readings.
>
> The standard deviation for the data is about 55 counts.
>
> The plot looks to my eye to be a nice Gaussian shape, so I assume that the
> deviations are caused mainly by (white?) noise.  There does not look to be
> much other structure in the shape of the data.  (Comments welcome.)
>
> Sorry for the long introduction, there are some questions coming!
>
> I have looked for information on the web about others who may have done
> this kind of PLL, but did not find much.
>
> Does anyone know of any articles related to this?
>
> If so, do you know what kind of performance they got?
>
> What kind of statement could I make about the 'stability' of this
> circuit?  Simplistically: a 'stability' of ~50 counts in 10e6 is ~5e-7?
>
> By the way, this performance is WAY WAY beyond what I was expecting
>
> Cheers,
>
> Scott
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Re: [time-nuts] HP5061B Ion Current

[paul swed]

I am listening and learning. Great point on the HV supplies.
When I look at the supplies I believe they are soldered cans. Is that
correct?

Further had not thought about the ionizer. Skips pictures of the CBT tube
clearly shows a popped ionizer.

There are two oven controllers AC or the DC version. I would strongly
believe the DC is quite easy to control through a FET and monostable. But
this approach simply prevents multiple trips if the ION pump is re-cycling.
AC maybe a bit harder. Have to actually look.

On Frankenstein I built a DC controller not realizing HP used DC in later
models so on that unit its very easy to do a soft start ramp.

Regards
Paul
WB8TSL


On Wed, Mar 22, 2017 at 9:33 AM, Scott McGrath  wrote:

> John makes a good point about the ionizer filament has anyone done a 'slow
> start' system for the Ionizer filament?
>
> I.e. Limit the inrush current as is done for expensive high power
> transmitting tubes?
>
>
>
>
> > On Mar 21, 2017, at 9:44 PM, Donald E. Pauly 
> wrote:
> >
> > It looks like that there is about 10% hysteresis on the cesium trip
> > off/on. That may not be enough to prevent cycling on and off.   I may
> > not have made it clear but instability in the +3,500 voltage makes a
> > big difference in the threshold ion current required for activation.
> > If it fades it can require a 10 uA smaller ion current to activate
> > cesium.
> >
> > -- Forwarded message --
> > From: John Miles 
> > Date: Tue, Mar 21, 2017 at 5:41 PM
> > Subject: Re: [time-nuts] Fwd:  HP5061B Ion Current
> > To: Discussion of precise time and frequency measurement
> > , rwa...@aol.com
> >
> >
> > That's some very nice work, Donald.  Looking back, I have junked one
> > or two Cs tubes that might have been usable if I'd thought through the
> > problem of high ion pump current as you and KB7APQ seem to have done.
> >
> > Another good reason to raise the lockout threshold would be to cut
> > down on the repetitive ionizer filament cycling that the tube will
> > otherwise undergo when you first fire up the oven.  That phenomenon
> > always makes me rally nervous.
> >
> > -- john, KE5FX
> > Miles Design LLC
> >
> >> -snip-
> >> When we overrode the cesium lockout at 29 μA or so of ion current, we
> >> needed only minor front panel adjustments for beam current of 20 μA.
> >> (We shorted across A15 R-4.) Our last ion current before power supply
> >> modifications at risen to 39 uA.  Beam current has been stable.
> >>
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Re: [time-nuts] Time Dilation tinkering

[jimlux]

On 3/22/17 12:04 AM, Michael Wouters wrote:

Dear Chris,

I believe IATA prohibits the carriage of any quantity of rubidium on
passenger aircraft.
You have to complete a "Dangerous Goods Declaration" and it then has
to go by cargo aircraft.



I imagine there's a "de minimis" quantity.  We didn't declare the cesium 
in the CSAC that we hand carried, and I'm pretty sure people have hand 
carried SRS Rb sources.


off of the MSDS from Symmetricom/Microsemi

"All Symmetricom’s rubidium product can be shipped both domestically and 
internationally as a non-hazardous product. Symmetricom has received 
letters of interpretation from both the United States Department of 
Transportation (US DOT)Ref. No. 08-0154 and the International Air 
Transport Association(IATA) stating that Symmetricom’s rubidium product 
are not considered a hazardous Class 4 material in transportation.




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Re: [time-nuts] Time Dilation tinkering

[William H. Fite]

Unhappily, local TSA authorities have--or at least appropriate to
themselves--the prerogative to disregard prior approvals from their
superiors. A former colleague of mine used to hand carry an ultra-high
precision gas dilutor between research sites. She had written approvals
from TSA in DC that included written specifications and interior/exterior
photographs of the electromechanical device. She never had any issues until
one occasion in Wilmington, NC, when a supervisor glanced contemptuously at
her documents and then opened (and irreparably damaged) the measurement
cell to the tune of ~$20K in repairs. A formal complaint to TSA generated a
pro forma letter of apology with a polite refusal to pay the repair cost.

A similar incident occurred some months later in Sacramento. On that
occasion, she literally threw her 60 year old, 97 pound, silver-haired body
across the device, saying that they could arrest her but they would not
destroy another instrument. Airport police were summoned, one of whom had a
lick of sense. He and an indignant TSA 3-striper went off to the phone,
taking her documents, university ID, and passport, the police lieutenant
first telling his officers to prevent the TSA people from touching the
instrument. Half an hour later, they were back, accompanied by a TSA suit
who apologized profusely and personally accompanied her to her gate.

Herman Wouk once described the Navy as a master plan designed by geniuses
for execution by idiots. The TSA seems to have been created in the same
factory.



On Wednesday, March 22, 2017, jimlux  wrote:

> On 3/21/17 7:12 PM, Chris Albertson wrote:
>
>> "flight" there is the word.Why drive up a mountain?   Take the clock
>> with you inside the pressurized cabin of a commercial airliner next time
>> you are on one of those 10 hour trans=pacific flights.   You be taller
>> then
>> any mountain and it is actually cheaper then a weather balloon.
>>
>> Can you get a Rb clock past the TSA x-ray machine.   Maybe if you ask
>> first.  There must be a way to hand cary specialized equipment.
>>
>>
>>
> I hand carry specialized equipment all the time and let it go through the
> x-ray.   About 1 time out of 10, they'll ask to open it up so they can swab
> it for the explosives residue ion mobility machine. Nothing looks as
> suspicious as a big block of something with two wires come out of it (i.e.
> a 7Amp-hour 12V lead acid battery).
>
> In fact, I did it yesterday with an unlabeled black pelican case holding a
> 8x10" PC board with a bunch of cards stacked on it.
>
>
> While I have my NASA ID and a shipping document describing it, I've never
> had to show either. Driver's license, 55 year old guy who looks like an
> engineer, and so forth, so maybe I don't look like the notional threat?
>
>
> When we hand carry "flight hardware" we do put it in a QA sealed (tape)
> antistatic bag, in a QA sealed container, with a special letter that's been
> coordinated 24 hours before with TSA. And we don't let it go through the
> X-ray (although not for any good reason that I know..). There's some
> process you're supposed to follow if they insist on opening it so you show
> up at the airport hours ahead of time.
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>


-- 
William H Fite, PhD
Independent Consultant
Statistical Analysis & Research Methods
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Re: [time-nuts] Time Dilation tinkering

[Bert Kehren via time-nuts]

I remember a time when some at PBT referred to the HP5065A as their  
precision pressure sensor
Bert Kehren
 
In a message dated 3/22/2017 10:03:58 A.M. Eastern Daylight Time,  
kb...@n1k.org writes:

Hi

In this case, the vacuum might work against you. You  change the pressure 
outside
the package and you get a flex. Flex translates  to dimensional changes. 
That gives you
a frequency shift. People make  absolute pressure sensors this way :) Rb’s 
are by no 
means the only  frequency standard impacted by this effect. Precision OCXO’
s have the
same  issue.

If you had enough room inside the package, you could do a “can  in a can” 
sort of approach. 
The outer vacuum sealed can flexes. The inner  vacuum sealed can does not 
see anything. 
You don’t eliminate the  sensitivity this way, you do attenuate it quite a 
bit with each layer. 
The  question then becomes - is is worth the increase in size? Since the 
pressure  sensitivity 
is well below many other environmental factors …. probably  not.

Bob

> On Mar 22, 2017, at 1:04 AM, jimlux   wrote:
> 
> On 3/21/17 4:29 PM, Hal  Murray wrote:
>> 
>> scmcgr...@gmail.com  said:
>>> However CSAC not subject to barometric effects as Rb  units are
>> 
>> Does anybody tried to measure CSAC vs  pressure?
>> 
>> 
>> 
> The physics package  in a CSAC is a vacuum, so it probably won't make 
much difference.
>  
> But, as a practical matter, I have a system with a CSAC going through  
thermal vacuum testing as I write this. We'll get some test data and we can  
compare the frequency against GPS and a OCXO at room temp/pressure, and at  
various temps in vacuum.
> 
> Remind me in 2 weeks, and I should  have the data plotted.
> 
> 
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Re: [time-nuts] Time Dilation tinkering

[jimlux]

On 3/22/17 4:04 AM, Angus wrote:

On Tue, 21 Mar 2017 13:08:56 +0100, you wrote:


On Tue, 21 Mar 2017 13:38:51 +1100
Hugh Blemings  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:
1) Stabilize or compensate for environmental effects (temperature, air pressure)
2) Build ensembles of Rb clocks.



Hi,

Looking back at an old plot I did of a temperature controlled and air
pressure compensated LPRO against an M12+T, the Hadamard Deviation of
the 1000s averages of the 1PPS measurement was about 5E-14 at 1 day.
A large part of that was likely the GPS, so with a better rubidium
like an FRK-H in a sealed and temperature controlled enclosure you
might be around 1E-14 at 1 day.

The bit that I'm not so sure about is the travelling. A long period of
movement, vibration, magnetic  fields, etc. all adding in could
obscure the effects of time dilation.

It might be quite possible, although a nearby mountain and a friend
with a helicopter would make it a lot easier!



No tall mountains in Australia, but...

Pikes Peak in the US is 14114 ft, 4304m and has a road to the top. Of 
course the base is at about 5000 ft/1600 m


In EU, there's probably a Seilbahn of some sort pretty high up in the 
Alps, although probably not to 4000m.




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Re: [time-nuts] Time Dilation tinkering

[jimlux]

On 3/21/17 10:36 PM, Michael Wouters wrote:

Yes, that's what I was quoted by the Microsemi agent and the price on
Mouser is similar.
The $1568 version was EOL'ed in December 2016; the more expensive unit is
the '2nd generation'.


Ah probably the one that has a good seal and has a rated temperature 
wider than 0-35C.



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Re: [time-nuts] Time Dilation tinkering

[Scott McGrath]

Ive been playing with one for work for the past few weeks and the Nor Easter 
which blew through NE did not affect short term ADEV with Tau < 1000s and that 
had a signficant drop in local barometric pressure for several hours

As to long term controlled studies no have not had opportunity to do so yet so 
that was an off the cuff observation based on the storm and not scientific data.

I'd be interested in any other observations around the same time though if 
anyone else is running a CSAC in NE


> On Mar 21, 2017, at 8:25 PM, Bob Camp  wrote:
> 
> Hi
> 
> Ummm … e …. it’s a gas cell standard. I’d bet there is a pressure effect.
> 
> Bob
> 
>> On Mar 21, 2017, at 7:01 PM, Scott McGrath  wrote:
>> 
>> Noted
>> 
>> However CSAC not subject to barometric effects as Rb units are
>> 
>> Content by Scott
>> Typos by Siri
>> 
 On Mar 21, 2017, at 4:18 PM, jimlux  wrote:
 
 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.
>>> ___
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Re: [time-nuts] PLL performance?

[Attila Kinali]

On Tue, 21 Mar 2017 21:10:19 -0400
David Scott Coburn  wrote:

> > What information are you looking for?
> 
> I was curious if anyone else has tried to do a PLL with two 0.5 Hz signals.  
> Does not seem like a particularly popular pastime!  I did find a few articles 
> which used a digital PLL to lock a OCXO to GPS at 1 Hz.

[...]

> I was interested in doing this as an analog PLL, for the challenge.  I've 
> done 
> my time on microprocessors and microcontrollers!


There have been a couple of discussions about doing GPSDOs using only analog
components in the past. People fare more knowledgable than me have commented
there on what the challenges would be and how to solve them. So I recommend
to go through the archives and look for those discussions. They might be a
little bit hidden, though.

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
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Re: [time-nuts] HP5061B Ion Current

[Scott McGrath]

John makes a good point about the ionizer filament has anyone done a 'slow 
start' system for the Ionizer filament?   

I.e. Limit the inrush current as is done for expensive high power transmitting 
tubes?




> On Mar 21, 2017, at 9:44 PM, Donald E. Pauly  wrote:
> 
> It looks like that there is about 10% hysteresis on the cesium trip
> off/on. That may not be enough to prevent cycling on and off.   I may
> not have made it clear but instability in the +3,500 voltage makes a
> big difference in the threshold ion current required for activation.
> If it fades it can require a 10 uA smaller ion current to activate
> cesium.
> 
> -- Forwarded message --
> From: John Miles 
> Date: Tue, Mar 21, 2017 at 5:41 PM
> Subject: Re: [time-nuts] Fwd:  HP5061B Ion Current
> To: Discussion of precise time and frequency measurement
> , rwa...@aol.com
> 
> 
> That's some very nice work, Donald.  Looking back, I have junked one
> or two Cs tubes that might have been usable if I'd thought through the
> problem of high ion pump current as you and KB7APQ seem to have done.
> 
> Another good reason to raise the lockout threshold would be to cut
> down on the repetitive ionizer filament cycling that the tube will
> otherwise undergo when you first fire up the oven.  That phenomenon
> always makes me rally nervous.
> 
> -- john, KE5FX
> Miles Design LLC
> 
>> -snip-
>> When we overrode the cesium lockout at 29 μA or so of ion current, we
>> needed only minor front panel adjustments for beam current of 20 μA.
>> (We shorted across A15 R-4.) Our last ion current before power supply
>> modifications at risen to 39 uA.  Beam current has been stable.
>> 
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Re: [time-nuts] Time Dilation tinkering

[Angus]

On Tue, 21 Mar 2017 13:08:56 +0100, you wrote:

>On Tue, 21 Mar 2017 13:38:51 +1100
>Hugh Blemings  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:
>1) Stabilize or compensate for environmental effects (temperature, air 
>pressure)
>2) Build ensembles of Rb clocks.
>

Hi,

Looking back at an old plot I did of a temperature controlled and air
pressure compensated LPRO against an M12+T, the Hadamard Deviation of
the 1000s averages of the 1PPS measurement was about 5E-14 at 1 day. 
A large part of that was likely the GPS, so with a better rubidium
like an FRK-H in a sealed and temperature controlled enclosure you
might be around 1E-14 at 1 day.

The bit that I'm not so sure about is the travelling. A long period of
movement, vibration, magnetic  fields, etc. all adding in could
obscure the effects of time dilation. 

It might be quite possible, although a nearby mountain and a friend
with a helicopter would make it a lot easier!

Angus.
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Re: [time-nuts] Time Dilation tinkering

[Bob Camp]

Hi

In this case, the vacuum might work against you. You change the pressure outside
the package and you get a flex. Flex translates to dimensional changes. That 
gives you
a frequency shift. People make absolute pressure sensors this way :) Rb’s are 
by no 
means the only frequency standard impacted by this effect. Precision OCXO’s 
have the
same issue.

If you had enough room inside the package, you could do a “can in a can” sort 
of approach. 
The outer vacuum sealed can flexes. The inner vacuum sealed can does not see 
anything. 
You don’t eliminate the sensitivity this way, you do attenuate it quite a bit 
with each layer. 
The question then becomes - is is worth the increase in size? Since the 
pressure sensitivity 
is well below many other environmental factors …. probably not.

Bob

> On Mar 22, 2017, at 1:04 AM, jimlux  wrote:
> 
> On 3/21/17 4:29 PM, Hal Murray wrote:
>> 
>> scmcgr...@gmail.com said:
>>> However CSAC not subject to barometric effects as Rb units are
>> 
>> Does anybody tried to measure CSAC vs pressure?
>> 
>> 
>> 
> The physics package in a CSAC is a vacuum, so it probably won't make much 
> difference.
> 
> But, as a practical matter, I have a system with a CSAC going through thermal 
> vacuum testing as I write this. We'll get some test data and we can compare 
> the frequency against GPS and a OCXO at room temp/pressure, and at various 
> temps in vacuum.
> 
> Remind me in 2 weeks, and I should have the data plotted.
> 
> 
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Re: [time-nuts] WTB: GPSDO

[Thomas Petig]

Hi Tim,

On Tue, Mar 21, 2017 at 06:36:51PM -0700, Tim Lister wrote:
> [...]
> I have a Symmetricom 58532A GPS antenna which has a N female connector
> but my 3 current GPS receivers all have SMA female connectors. If I
> want to provide capacity for at least 4 receivers fed from the same
> antenna, I was wondering what the best option for a splitter and where
> to do the N-to-SMA conversion. I currently have a Mini-Circuits
> ZAP3PD-2 power splitter which does SMA input to 3 SMA outputs. This
> seems to work but the connected devices all complain of an Antenna
> short, which doesn't seem good. The other popular option seems to be
> the Symmetricom 58536A 1x4 splitter which would then require 3-4
> N-to-SMA cables - it looks like although this has gain, it seems to be
> more of "eliminating loss" than straight gain so would presumably not
> overpower the receivers' frontends. Or maybe there is another more
> suitable SMA splitter in the Mini Circuits confusingly extensive
> catalog ?
Your splitter looks ok, but it has DC pass through on all ports. I would
recommend to put DC-blocks on all but one. The problem is all your
receiver want to power up the antenna and deliver around 3 to 5 V supply
Voltage on the port, your splitter is short-circuit them, which is not
good, especially if the voltage does not match. (The minicircuits
datasheet for the ZA3PD-2+, I guess that is the one you meant,  says
RF+DC on all ports) The short-circuit might damage your receiver.

If you take a splitter without DC pass through, you will need an
additional bias-T to feed some supply voltage again.

The special GNSS splitters forward DC only from one port and provide
some 200 Ohm DC termination together with the DC-block on the other
ports to keep the receiver happy, i.e., it seems current consumption and
therefore believes the antenna is ok. Some have an amplifier to
compensate for the loss of the splitter, but it is not necessary if the
antenna delivers enough.

So the GNSS splitter is electrically, a splitter like you have, a
separate LNA in front and all but one port with a bias-T (in reverse,
this provides the DC-block and ensures the signal is not 200 Ohm
terminated) where the DC connector has 200 Ohm termination.

I personally use a NARDA 4372A-4 (10 Euros on Ebay) with three DC-blocks
from minicircuits to split the GNSS signals and a good outdoor antenna.

Best,
   Thomas, DK6KD/SA6CID


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Re: [time-nuts] PLL Digital Loop Filter

[Attila Kinali]

On Tue, 21 Mar 2017 21:45:24 -0400
Bob Camp  wrote:

> 1) You need a way to digitize the phase input with adequate resolution. If 
> you have a 1 second period and want 1 ns, you need a way to digitize at
> a 1:1,000,000,000 sort of level. That’s in the 30 bit range so a simple
> ADC isn’t going to do it alone. 

That depends on how the phase difference is measured. If the whole
measurement period needs to be encoded, then yes, the number of
bits needed will make it difficult. But usually the input frequency
range is limited, which allows to measure and encode just the difference
between expected and actual arrival time of the pulse/edge. The integrated
version of these PLLs (the ADPLL - all digitall PLL), if they have a
real TDC, have only a resolution in the order of 7-8 bits (IIRC I've seen
down to 4 bits). And then there is the class of those Bang-Bang PLL,
which only encode one bit: early/late. Eventhough they are relatively
crude and rely on the loopfilter to smooth things out, they perform
quite well. 

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
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Re: [time-nuts] Time Dilation tinkering

[jimlux]

On 3/21/17 7:12 PM, Chris Albertson wrote:

"flight" there is the word.Why drive up a mountain?   Take the clock
with you inside the pressurized cabin of a commercial airliner next time
you are on one of those 10 hour trans=pacific flights.   You be taller then
any mountain and it is actually cheaper then a weather balloon.

Can you get a Rb clock past the TSA x-ray machine.   Maybe if you ask
first.  There must be a way to hand cary specialized equipment.




I hand carry specialized equipment all the time and let it go through 
the x-ray.   About 1 time out of 10, they'll ask to open it up so they 
can swab it for the explosives residue ion mobility machine. Nothing 
looks as suspicious as a big block of something with two wires come out 
of it (i.e. a 7Amp-hour 12V lead acid battery).


In fact, I did it yesterday with an unlabeled black pelican case holding 
a 8x10" PC board with a bunch of cards stacked on it.



While I have my NASA ID and a shipping document describing it, I've 
never had to show either. Driver's license, 55 year old guy who looks 
like an engineer, and so forth, so maybe I don't look like the notional 
threat?



When we hand carry "flight hardware" we do put it in a QA sealed (tape) 
antistatic bag, in a QA sealed container, with a special letter that's 
been coordinated 24 hours before with TSA. And we don't let it go 
through the X-ray (although not for any good reason that I know..). 
There's some process you're supposed to follow if they insist on opening 
it so you show up at the airport hours ahead of time.

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Re: [time-nuts] Time Dilation tinkering

[Michael Wouters]

Hmm, it appears that Symmetricom has an interpretation from IATA which
classifies their rubidium-containing products as non-hazardous.

I went through all of this some time ago because we were shipping
rubidiums about domestically (Australia) and there was no permissible
maximum qty of rubidium allowed on a passenger aircraft. It doesn't
make sense: any event which might have caused exposure of the rubidium
in a clock to water, was likely rather more severe than the effects of
less than 1 gram of rubidium igniting. Hard to argue these things
though.

Cheers
Michael
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Re: [time-nuts] Time Dilation tinkering

[Michael Wouters]

Dear Chris,

I believe IATA prohibits the carriage of any quantity of rubidium on
passenger aircraft.
You have to complete a "Dangerous Goods Declaration" and it then has
to go by cargo aircraft.

Cheers
Michael


On Wed, Mar 22, 2017 at 1:12 PM, Chris Albertson
 wrote:
> "flight" there is the word.Why drive up a mountain?   Take the clock
> with you inside the pressurized cabin of a commercial airliner next time
> you are on one of those 10 hour trans=pacific flights.   You be taller then
> any mountain and it is actually cheaper then a weather balloon.
>
> Can you get a Rb clock past the TSA x-ray machine.   Maybe if you ask
> first.  There must be a way to hand cary specialized equipment.
>
>
>
> On Tue, Mar 21, 2017 at 7:03 PM, Tom Van Baak  wrote:
>
>>
>> But attached is one of the first plots where I put a SA.32m in a home-brew
>> vacuum chamber and pulled down to a few inches of Hg for a few hours to
>> simulate the low pressure of a flight up to 50 or 90,000 ft. For a high
>> altitude relativity experiment -- where you'd like your clock to remain
>> stable to parts in e-13 and not accumulate too many stray ns -- it's not a
>> good sign when your clock changes by 2e-11 (that's more than 1 ns per
>> minute) just because of ambient pressure changes.
>>
> --
>
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] True Time Nut Mission: NASA's Deep Space Atomic Clock (DSAC)

[Bill Byrom]

NASA's Deep Space Atomic Clock test mission is moving toward a late-2017
launch (don't all projects slip?). The DSAC was just integrated with the
spacecraft. The clock uses a ~40.5 GHz hyperfine transition of mercury
ions. This steers an ovenized crystal USO (Ultra Stable Oscillator) from
FEI with 1-100 sec stability <2e-13 and drift <1e-10/day. A GPS receiver
is also on board:
https://www.jpl.nasa.gov/news/news.php?feature=6784

NASA information about the DSAC applications at:
https://www.nasa.gov/mission_pages/tdm/clock/index.html

Expected DSAC performance (2014 paper). This paper claims an estimated
Allan Deviation of <1e-14 (perhaps 3e-15) at a one day interval when in
space:
https://www.researchgate.net/publication/260036335_Expected_Performance_of_the_Deep_Space_Atomic_Clock_Mission


Here are the latest two papers I can find (from Feb 2016):

** Deep Space Atomic Clock Technology Demonstration Mission Onboard
Navigation Analog Experiment:
https://www.researchgate.net/publication/293648952_Deep_Space_Atomic_Clock_Technology_Demonstration_Mission_Onboard_Navigation_Analog_Experiment

** Preliminary Investigation of Onboard Orbit Determination using Deep
Space Atomic Clock Based Radio Tracking:
https://www.researchgate.net/publication/293648187_Preliminary_Investigation_of_Onboard_Orbit_Determination_using_Deep_Space_Atomic_Clock_Based_Radio_Tracking

--
Bill Byrom N5BB

- Original message -
From: Gregory Beat 
To: time-nuts@febo.com
Subject: [time-nuts] True Time Nut Mission: NASA's Deep Space Atomic
Clock (DSAC)
Date: Tue, 12 Jan 2016 17:31:26 -0600

Upcoming Event: Deep Space Atomic Clock
Jan. 14, 2016, at 7 p.m. PT (10 p.m. ET, 0300 UTC)
You can watch this event via USTREAM:  http://www.ustream.tv/NASAJPL2

Speakers: 
Todd Ely, DSAC Principal Investigator, JPL
Allen H. Farrington, DSAC Project Manager, JPL
http://www.nasa.gov/mission_pages/tdm/clock/clock_overview.html#.VpWMgK9OKK0
Atomic clocks are an integral, yet almost invisible component of modern
life. 
For space exploration, they have been the foundational frequency
standard for NASA's Deep Space Network. NASA's Deep Space Atomic Clock
(DSAC) Technology Demonstration Mission, led by the Jet Propulsion
Laboratory, has been maturing the latest Atomic Clock technologies into
a smaller package, suitable for installation on a variety of deep space
probes to enhance navigation precision and gravity science across the
solar system.

DSAC is scheduled for launch in mid-2016.  
Satellite being built by Surrey Satellite Technologies USA, Englewood,
CO


Sent from iPad Air
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Re: [time-nuts] Time Dilation tinkering

[Hugh Blemings]

Hi,

My profound thanks to Tom, Bob, Chris, Attila, Scott, Jim, Hal and 
Michael for such thorough and thoughtful replies to my initial post.


I'm fortunate enough to know some of the local amateur high altitude 
balloon crowd and had contemplated such an endeavour but note this 
wouldn't be feasible due to the pressure and temperature sensitivities 
of the Rb sources.


I had also thought the weight limitations might be a factor - an ardunio 
and a battery one thing to slow if things go wrong, a Rb clock and other 
bits a whole nother can of worms :)


I will still pick up one of the surplus Rb units and tinker with it, my 
GPSDO and my TAPR TICC that arrived the other day.


Slightly more pedestrian (but equally fun :) construction projects ahead 
I'm sure - keeping things stable in my garage in an Australian summer 
may yet prove challenge enough ;)


Thanks again

vy 73
Hugh
VK3YYZ/AD5RV


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Re: [time-nuts] Time Dilation tinkering

[Michael Wouters]

Yes, that's what I was quoted by the Microsemi agent and the price on
Mouser is similar.
The $1568 version was EOL'ed in December 2016; the more expensive unit is
the '2nd generation'.

Cheers
Michael

On Wed, 22 Mar 2017 at 9:06 am, jimlux  wrote:

> 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.
>
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Re: [time-nuts] Time Dilation tinkering

[jimlux]

On 3/21/17 4:29 PM, Hal Murray wrote:


scmcgr...@gmail.com said:

However CSAC not subject to barometric effects as Rb units are


Does anybody tried to measure CSAC vs pressure?



The physics package in a CSAC is a vacuum, so it probably won't make 
much difference.


But, as a practical matter, I have a system with a CSAC going through 
thermal vacuum testing as I write this. We'll get some test data and we 
can compare the frequency against GPS and a OCXO at room temp/pressure, 
and at various temps in vacuum.


Remind me in 2 weeks, and I should have the data plotted.


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Re: [time-nuts] Time Dilation tinkering

[jimlux]

On 3/21/17 5:25 PM, Bob Camp wrote:

Hi

Ummm … e …. it’s a gas cell standard. I’d bet there is a pressure effect.



But the gas cell, the laser, etc. is in a vacuum - that's the "wear out" 
mechanism for a CSAC - the getter fills up, the pressure inside the 
vacuum package increases, and the heater can't keep it hot.


I'm speculating here... I don't really know enough about the guts of the 
CSAC to be sure.



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Re: [time-nuts] Time Dilation tinkering

[jimlux]

On 3/21/17 7:03 PM, Tom Van Baak wrote:

Yes, MAC and CSAC do show environmental sensitivity. But that should not be a 
surprise to anyone that works with precise time & frequency.

The factors include voltage, temperature, temperature gradient, pressure, 
humidity, acceleration, tilt (orientation), and who knows what else. Maybe even 
radiation? One looks for the *coefficient* of course, but also linearity, 
repeatability, hysteresis, and even interaction amongst factors. It's not an 
easy task to do this, nor can one assume each unit of a given make/model will 
be the same. I don't have comprehensive data or a nice report.

But attached is one of the first plots where I put a SA.32m in a home-brew 
vacuum chamber and pulled down to a few inches of Hg for a few hours to 
simulate the low pressure of a flight up to 50 or 90,000 ft. For a high 
altitude relativity experiment -- where you'd like your clock to remain stable 
to parts in e-13 and not accumulate too many stray ns -- it's not a good sign 
when your clock changes by 2e-11 (that's more than 1 ns per minute) just 
because of ambient pressure changes.




I wonder if the effect is due to vacuum, or something like thermal 
gradients (no convective heat transfer in vacuo)


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Re: [time-nuts] Time Dilation tinkering

[Chris Albertson]

"flight" there is the word.Why drive up a mountain?   Take the clock
with you inside the pressurized cabin of a commercial airliner next time
you are on one of those 10 hour trans=pacific flights.   You be taller then
any mountain and it is actually cheaper then a weather balloon.

Can you get a Rb clock past the TSA x-ray machine.   Maybe if you ask
first.  There must be a way to hand cary specialized equipment.



On Tue, Mar 21, 2017 at 7:03 PM, Tom Van Baak  wrote:

>
> But attached is one of the first plots where I put a SA.32m in a home-brew
> vacuum chamber and pulled down to a few inches of Hg for a few hours to
> simulate the low pressure of a flight up to 50 or 90,000 ft. For a high
> altitude relativity experiment -- where you'd like your clock to remain
> stable to parts in e-13 and not accumulate too many stray ns -- it's not a
> good sign when your clock changes by 2e-11 (that's more than 1 ns per
> minute) just because of ambient pressure changes.
>
-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] PLL performance?

[David Scott Coburn]

The loop filter does have a very low bandwidth, of the order you mentioned.

The lock time is surprisingly quick, but one man's pocket change may be another 
man's fortune

I use a lag-lead filter with the PC2 comparator.  It begins to 'track' after a 
minute or so.

>From a cold start there is one large overshoot with the VCO frequency starting 
>too low and then going high.  On the scope  you can then watch the VCO  0.5 Hz 
>signal slowly sidle up to the reference 0.5 Hz signal over the course of a few 
>more minutes.

It does take 10 or 15 minutes for it to settle to where the jitter is down into 
the 5th or 6th digit on my frequency counter though.

Scott

On Tuesday, March 21, 2017 12:14:15 PM EDT M. Simon via time-nuts wrote:up to
> To get your loop to lock and keep phase noise down the loop filter would
> need a bandwidth of .05 Hz or less. That would mean long lock times. Very
> long lock times. Engineering is the art of making what you want from what
> you can get at a profit. I like Polywell Fusion.
> 
> 
> On Tuesday, March 21, 2017 2:01 AM, David Scott Coburn
>  wrote:
> 



> 
> 
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Re: [time-nuts] PLL performance?

[David Scott Coburn]

Thanks Tom.

Scott

On Tuesday, March 21, 2017 2:08:14 AM EDT Tom Van Baak wrote:
> Andy, Bill, et al.
> 
> Attached is a GIF version of Scott's (unreadable?)
> histogram-utcday21613x.pdf file.
> 
> /tvb
> 
> - Original Message -
> From: "Andy" 
> To: "Discussion of precise time and frequency measurement"
>  Sent: Tuesday, March 21, 2017 12:23 AM
> Subject: Re: [time-nuts] PLL performance?
> 
> > Second file successfully opened in Irfanview.
> > 
> > Three other PDF readers, including Adobe, could not open it.
> > 
> > Andy


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Re: [time-nuts] PLL performance?

[David Scott Coburn]

On Tuesday, March 21, 2017 12:22:46 PM EDT Tom Van Baak wrote:
> Hi Scott,
> 
> That's a nice project.
> 
> Combining quartz and pendulum like that is essentially how a GPSDO works. In
> your case, instead of a 10 MHz oscillator you have a 1 MHz oscillator and
> instead of 1PPS you have 1/2 PPS. Whether you use an analog loop or a
> digital loop there are dozens of examples on the web and hundreds of
> time-nuts postings that cover this territory.

I've looked for some, but did not find much.  I guess I am not using the right 
search terms?

(Lots of PLL information on the web.  Was having trouble finding others who had 
done this syncing of two 0.5 Hz, or similar, signals.)

> Note that you have a choice of using the hp 107a quartz oscillator to
> discipline the pendulum, or use the pendulum to discipline the quartz. Each
> project has a certain charm.

This is part of a larger long-term project to build a precision dual pendulum 
set.  The HP 107A will probably be involved in the instrumentation for 
monitoring the pendulums.  (This is the subject of another posting later on.)
 
> Your decision to use a 32-bit time stamping counter (TSC) is good. Pendulum
> clocks tend to be less accurate than quartz oscillators and so they tend to
> "wrap" more often. A TSC avoids the zero boundary, sign, and sample rate
> issues that can plague a traditional start/stop, aka time interval counter
> (TIC).

The TSC works very well.

> A standard deviation of ~50 counts out to 10 million counts over a day
> represents a consistency or stability of 50 / 1e7 or 5e-6 or 5 ppm at "tau"
> 1 day. I would guess the shape of your Gaussian merely reflects the loop
> parameters you have chosen, and not so much the quality of the 1 MHz quartz
> or the 0.5 Hz pendulum. For example, tighten the loop and I bet your
> histogram will narrow.
> 
> I'm not sure of your terminology -- at one point you mention 1 MHz, then
> mention 10,000,000, then mention 10e6, which some people might read as 10^6
> as in 1,000,000 or 1e6 and others may read as 10x10^6, as in 10^7 or
> 10,000,000 or 1e7.

I guess this was a bit confusing.  The 1 MHz is generated by the VCO.  The 
10,000,000 comes from counting the 5 MHz signal for 2 seconds.  The 10e6 was 
intended to represent 10,000,000, but I see that would have been more clear as 
10^7.

> Either way, this level of performance for a hp 107 oscillator or for a
> pendulum clock seems right. I don't think there's any problem with your
> setup. Pendulum clocks can easily get to ppm levels; some even get to ppb
> levels.

I was imagining that, to a first order, the stability of the HP 107A would not 
show up in the histogram to a noticeable degree over the course of the day.  
(If it drifts by 10^-12 during the day this would be only about 1/2 of a single 
5 MHz cycle?)

I was assuming that for this purpose the HP 107A was 'perfect' and all of the 
jitter shown on the histogram is from the instability of the VCO.
 
> One suggestion is for you to make several runs against an independent
> reference: 1) hp 107A only, 2) pendulum only, 3) hp 107A and pendulum with
> PLL. When you see these ADEV plots you will get a hint of how the PLL
> should be tuned. Here's a classic example:

I don't have the pendulums yet!  :)

I did run the setup with the PLL out of the loop.  That is, just running the 
reference 0.5 Hz into the TSC.  This gives me an endless stream of mildly 
uninteresting 10^7 readings..  (However, it does show that my TSC 
triggering and latching circuits are working correctly.)

> 
> http://www.thinksrs.com/assets/instr/PRS10/PRS10diag2LG.gif
> 
> Some additional GPSDO, pendulum/PLL, pendulum ADEV links:
> 
> http://leapsecond.com/pages/gpsdo/
> 
> http://leapsecond.com/hsn2006/

I hope to be generating plots like this some day.

> 
> /tvb

Cheers,

Scott

> - Original Message -
> From: "David Scott Coburn" 
> To: 
> Sent: Monday, March 20, 2017 6:07 PM
> Subject: [time-nuts] PLL performance?
> 



> 
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Re: [time-nuts] PLL performance?

[David Scott Coburn]

Ack!  Sorry for the questionable PDF file.  It was generated by gnuplot on my 
Linux system.

I see that Tom has posted a gif of the image, so I won't duplicate it.

Cheers,

Scott

On Monday, March 20, 2017 10:36:05 PM EDT Bill Byrom wrote:
> Hi, Scott. I rarely post here, but just noticed your post. I can open
> the "PLL0.pdf" file, but the other files appears to be corrupted. Adobe
> Acrobat Reader thinks it's not really a PDF file or it's corrupted. I'm
> not ready to comment on the expected results yet, and would like to see
> the histogram.
> 
> Are you using phase detector 1 or 2? What are the details for your loop
> filter?
> 
> --
> Bill Byrom N5BB
>
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Re: [time-nuts] PLL performance?

[David Scott Coburn]

On Tuesday, March 21, 2017 12:26:59 PM EDT Attila Kinali wrote:
> Moin,
> 
> On Mon, 20 Mar 2017 21:07:03 -0400
> 
> David Scott Coburn  wrote:
> > I have built and tested a PLL circuit that will be used to generate a 1
> > MHz
> > signal locked to a 0.5 HZ signal from a pendulum.  (Details available upon
> > request.)
> 
> [...]
> 
> > I tested this by feeding the 0.5 Hz output of the PLL into a "time-stamp
> > counter" board which I built to go into an HP 3582A Data Acquisition unit.
> > 
> >  The TSC uses the 5 MHz signal from the HP 107A to feed a free-running
> >  32-bit> 
> > binary counter.  The 0.5 Hz input latches the count value (on the rising
> > edge of the signal), which is then logged.
> 
> The VCO in the 4046 is an odd mixture between a relaxation and an
> delay line oscillator. It's stability is not that good (at least
> not by modern standards). As such, your phase comparator frequency
> of just 0.5Hz is too low for the 4046 to show its peak performance,
> as it is basically free running for 2s before a slight correction
> is applied. Usually the frequencies used for a 4046 are in the range
> of 1kHz to 100kHz.
> 
> Alternatively, you can dissable the internal VCO (inhibit pin) and
> use an external oscillator that is more stable. The VCXOs by Abracon
> (ASVTX-*) are readily available and cheap enough. If you use a 20MHz
> oscillator (e.g. ASVTX-09-20) divide the output first by 2 (using a
> D-flipflop) and then by 10 (e.g. using 74LV161)
> until you are at 1Hz, then use second D-flipflops to get to 0.5Hz.
> This gives you 1MHz inbetween.

I'll have a look at the ASVTX units.  Thanks!

> > The standard deviation for the data is about 55 counts.
> 
> This means that your jitter (at 0.5Hz) is 11µs RMS.
> 
> > The plot looks to my eye to be a nice Gaussian shape, so I assume that the
> > deviations are caused mainly by (white?) noise.  There does not look to be
> > much other structure in the shape of the data.  (Comments welcome.)
> 
> Yes, It looks very much Gauss shaped, it is very likely that this is
> indeed a Gauss process, but to be sure (in a statistical sense) you
> would need to do something like a qq-plot or similar to check,
> whether it's actually a Gaus distribution (there are others that
> look very similar). But for all practical purposes, that does not
> really matter.
> 
> Please be aware that a noise process can be Gaussian and not be white.
> E.g. 1/f-noise has a Gaussian distribution as well.
> 
> > I have looked for information on the web about others who may have done
> > this kind of PLL, but did not find much.
> > 
> > Does anyone know of any articles related to this?
> 
> What information are you looking for?

I was curious if anyone else has tried to do a PLL with two 0.5 Hz signals.  
Does not seem like a particularly popular pastime!  I did find a few articles 
which used a digital PLL to lock a OCXO to GPS at 1 Hz.

> > If so, do you know what kind of performance they got?
> 
> Your performance seem's ok, but limited by the VCO of the 4046.

It is OK, and better than I was expecting.  It is probably good enough for its 
intended purpose, but this being the time-nuts channel I will look into a 
better VCO.

> As your PLL frequency is very very low, you will face a lot of
> difficulties due to leakage and other non-idealities of the
> various components. I would recommend to use a digital PLL
> implemented in a uC (PIC, AVR32, ARM Cortex-M0/M3) instead.
> If you clock the uC from the 1MHz signal and use the
> capture/compare (aka timer) unit of the uC will give you
> a resolution in the region of 10-40ns, which should be good
> enough considering the noise/stability of the pendulum.
> With that you can easily implement a PLL with a loop time constant
> of several seconds without the fear of running into problems from
> the analog parts.

I was interested in doing this as an analog PLL, for the challenge.  I've done 
my time on microprocessors and microcontrollers!

> 
> 
>   Attila Kinali

Cheers,

Scott

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