Re: [time-nuts] Cesium Clock Avialable

[djl]

Hi Doug. Did not see my email go by. Would like to have the cs standard.
I'm visiting my family in Huntington Beach and can pick it up so no 
packing. Have cash.

Off list at djl at Montana dot com
Thanks Don AJ7LL


On 2018-05-18 22:04, Doug Millar via time-nuts wrote:

Hi, I am willing to part with my HP 5061A cesium standard and manual.
The unit was rebuilt and functioning some years ago and not used since
then. There is usable cesium in the tube and the unit worked. I have
not tested it recently. It has a Patek-Philippe analogue clock in the
front. The unit is in great physical condition.  Asking $600 plus
shipping from Long Beach, CA. 90806
I also have an ESI 242D resistance calibrator and a Julie primary
resistance standard in an oven. Let me know if you are interested.
Very reasonable.
 Thanks, Doug K6JEY
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Re: [time-nuts] Cesium Clock Avialable

[djl]

Hi Doug
I'm visiting just down the coast and could pick up the HP. If not sold 
I'll take it.

Don AJ7LL


On 2018-05-18 22:04, Doug Millar via time-nuts wrote:

Hi, I am willing to part with my HP 5061A cesium standard and manual.
The unit was rebuilt and functioning some years ago and not used since
then. There is usable cesium in the tube and the unit worked. I have
not tested it recently. It has a Patek-Philippe analogue clock in the
front. The unit is in great physical condition.  Asking $600 plus
shipping from Long Beach, CA. 90806
I also have an ESI 242D resistance calibrator and a Julie primary
resistance standard in an oven. Let me know if you are interested.
Very reasonable.
 Thanks, Doug K6JEY
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Re: [time-nuts] Better quartz crystals with single isotope ?

[djl]

Darn. maybe not grain boundaries, but dislocations? or both?
Don

On 2018-04-22 10:19, Poul-Henning Kamp wrote:

Silicon comes in a number of isotopes but 95% of it is Silicon-28.

When you make pure mono-crystaline silicon, you get 50-60% better
thermal conductivity if you only use Silicon-28 atoms.

Yes, you read that right:  50-60% improvement for removing the
remaining 5% other silicon isotopes, and for this and other reasons,
sorting silicon atoms by isotope is now a thing, which amongst other
side effects have made the Advogardo Project possible.

I can't help wonder if there may be similar interesting effects in
quartz crystals, if they were monoisotopic ?

Several relevant mechanisms can be imagined, lower internal damping,
higher stiffness etc. etc.

We know a LOT about quartz and have a very good theory for its
behaviours, but i find no signs anybody has ever touched monoisotopic
Quartz.

The obvious experiment is not rocket-science, nor does it demand
inordinate resources for amateurs, see for instance from 03:35:

https://archive.org/details/59554KrystallosCF

But it is clearly beyond what I have time to persue.

Do we know anybody in the quartz business who needs a really cool
research project ?

Poul-Henning


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Re: [time-nuts] Better quartz crystals with single isotope ?

[djl]

Interesting indeed!  Seems as if there ought to be info about drawing 
crystals mono vs poly isotopic somewhere out there. Also some info about 
crystal grain boundaries that might be generated in a zone furnace 
drawing by isotope inclusions. Seems the boundaries are responsible for 
the sudden frequency shifts? My solid state physics is evanescent, but 
there ought to be a TN with some info...

Don


On 2018-04-22 10:19, Poul-Henning Kamp wrote:

Silicon comes in a number of isotopes but 95% of it is Silicon-28.

When you make pure mono-crystaline silicon, you get 50-60% better
thermal conductivity if you only use Silicon-28 atoms.

Yes, you read that right:  50-60% improvement for removing the
remaining 5% other silicon isotopes, and for this and other reasons,
sorting silicon atoms by isotope is now a thing, which amongst other
side effects have made the Advogardo Project possible.

I can't help wonder if there may be similar interesting effects in
quartz crystals, if they were monoisotopic ?

Several relevant mechanisms can be imagined, lower internal damping,
higher stiffness etc. etc.

We know a LOT about quartz and have a very good theory for its
behaviours, but i find no signs anybody has ever touched monoisotopic
Quartz.

The obvious experiment is not rocket-science, nor does it demand
inordinate resources for amateurs, see for instance from 03:35:

https://archive.org/details/59554KrystallosCF

But it is clearly beyond what I have time to persue.

Do we know anybody in the quartz business who needs a really cool
research project ?

Poul-Henning


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Re: [time-nuts] Pulsars, clocks, and time nuts (Jim Palfreyman)

[djl]

Nice, Jim!!!

On 2018-04-13 01:54, Tom Van Baak wrote:

Amazing news... 1.2.3.

1) Many of you know that pulsars are weird astronomical sources of
periodic signals. Some are so accurate that they rival atomic clocks
for stability! True, but I don't have a 100 foot antenna at home so
I'll take their word for it. Plus, you have to account for a myriad of
PhD-level corrections: from earth's rotation to general relativity.
And, like quartz or rubidium clocks, pulsars drift (as they gradually
slow down). Precision timing is not easy. If you poke around the web
you can find numerous articles describing their detection and
measurement and exploring their use as reference clocks, both here and
potentially for deep-space timekeeping.

2) If you do a lot of clock measurement at home then you know the dark
side of working with precision clocks. There are signal quality
issues, measurement resolution issues, reference stability
limitations, offset, drift, phase jumps, frequency jumps, missed or
extra cycles, glitches, etc. For example, quartz oscillators
(depending on make / model / luck) can exhibit frequency jumps; i.e.,
without warning they just change frequency without your permission.
Ok, maybe not by a lot, but enough to notice; perhaps enough to cause
trouble to any naive GPSDO PID algorithm that assumes steady state
from the oscillator you thought was stable.

3) Now the exciting part! Fellow time-nut Jim Palfreyman studies
pulsars. You've seen postings from him now and then over the years. It
turns out Jim is the first person to catch a pulsar in the act of a
frequency jump. After 3 years of continuous searching! This is really
cool. Just amazing. You can't get more time nutty than this. And it
just got published in Nature. It's a perfect never-give-up,
i-eat-nanoseconds-for-breakfast, time nut thing to do. I am so
impressed.

To quote Jim:

On December 12, 2016, at approximately 9:36pm at night, my phone
goes off with a text message telling me that Vela had glitched. The
automated process I had set up wasn't completely reliable - radio
frequency interference (RFI) had been known to set it off in error.

So sceptically I logged in, and ran the test again. It was genuine!
The excitement was incredible and I stayed up all night analysing 
the data.


What surfaced was quite surprising and not what was expected. Right
as the glitch occurred, the pulsar missed a beat. It didn't pulse.

Here is a very readable description of his discovery:

http://theconversation.com/captured-radio-telescope-records-a-rare-glitch-in-a-pulsars-regular-pulsing-beat-94815

And also the official Nature article with all the juicy, peer-reviewed 
details:


https://rdcu.be/LfP0

So congratulations to Jim. I will think of him next time my 10811A
quartz oscillator does a frequency jump or next time my 60 Hz mains
frequency monitor skips a cycle...

If you have comments or questions feel free to send them to Jim
directly (see Cc: address). Perhaps he can summarize the questions and
his answers in a posting to time-nuts soon.

/tvb

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Re: [time-nuts] quartz / liquid nitrogen

[djl]

Tom: I sense a nice experiment!  Dry ice temps can be attained with 
modest Dewars and thermoelectric fridge devices. PID controller and 
bob's your uncle.  Type K thermocouple modules on epay.   With that 
apparat, a nice set of adev vs temperature possible?  Dry ice/acetone or 
ethyl alcohol (everclear) slurry is often used as a calibration point 
BTW. Liquid N2 may be too cold, or is it He I'm thinking of???

Don
On 2018-04-02 13:46, Tom Van Baak wrote:

Has anyone tried running a quartz oscillator at liquid nitrogen
temperatures: -196 C (-321F, 77K)? It's probably impractical
commercially, but maybe something of value to a time nut. Would that
dramatically lower temperature improve phase noise & short-term
performance? Is there a crystal cut that could be optimized for 77 K
instead of ~25 C (room) or 60 C (oven)?

If not Nitrogen, how about dry ice (-109F -78C)?

/tvb

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[time-nuts] Fwd: [New post] New Part Day: ATMegas With Programmable Logic

[djl]

 

nutters might find this of interest. 

Don 

 Original Message  

SUBJECT:
[New post] New Part Day: ATMegas With Programmable Logic

DATE:
2018-03-02 05:00

FROM:
Hackaday <comment-re...@wordpress.com>

TO:
d...@montana.com

REPLY-TO:
Hackaday 
<comment+_hf2r4gr8gmz_wtbebcty...@comment.wordpress.com>

 Brian Benchoff posted: "Since Microchip acquired Atmel, the fields of
battle have fallen silent. The Crusaders have returned home, or have
been driven into the sea. The great microcontroller holy war is over. As
with any acquisition, there is bound to be some crossover betwee" 

Respond to this post by replying above this line

NEW POST ON HACKADAY

NEW PART DAY: ATMEGAS WITH PROGRAMMABLE LOGIC [1]

 by Brian Benchoff [2] 

Since Microchip acquired Atmel, the fields of battle have fallen silent.
The Crusaders have returned home, or have been driven into the sea. The
great microcontroller holy war is over. 

As with any acquisition, there is bound to be some crossover between two
product lines. Both Atmel's AVR platform and Microchip's PICs have their
adherents, and now we're beginning to see some crossover in the weird
and wonderful circuitry and design that goes into your favorite
microcontroller, whatever that might be. The newest part from Microchip
is an ATMega with a feature usually found in PICs. This is a Core
Independent Peripheral. What is it? Well, it's kinda like a CPLD stuck
in a chip, and it's going to be in the new Arduino board. 

The ATMega4809 is the latest in a long line of ATMegas [3], and has the
features you would usually expect as the latest 8-bit AVR. It runs at
20MHz, has 48 K of Flash, 6 K of SRAM, and comes in a 48-pin QFN and
TQFP packages. So far, everything is what you would expect. What's the
new hotness? It's a Core Independent Peripheral in the form of
Configurable Custom Logic (CCL) that offloads simple tasks to hardware
instead of mucking around in software. 

So, what can you do with Configurable Custom Logic? There's an
application note for that [4]. The CCL is effectively a look-up table
with three inputs. These inputs can be connected to I/O pins, driven
from the analog comparator, timer, UART, SPI bus, or driven from
internal events. The look-up table can be configured as a three-input
logic gate, and the output of the gate heads out to the rest of the
microcontroller die. Basically, it's a tiny bit of programmable glue
logic. In the application note, Microchip provided an example of
debouncing a switch using the CCL. It's a simple enough example, and
it'll work, but there are a whole host of opportunities and
possibilities here. 

Additionally, the ATMega4809, "has been selected to be the on-board
microcontroller of a next-generation Arduino board" according to the
press release I received. We're looking forward to that new hardware,
and of course a few libraries that make use of this tiny bit of custom
programmable logic. 

BRIAN BENCHOFF [2] | March 2, 2018 at 4:00 am | Tags: atmega [5],
ATMega4809 [6], ccl [7], Configurable Custom Logic [8], LUT [9],
microchip [10], New Part Day [11] | Categories: Hackaday Columns [12],
hardware [13] | URL: https://wp.me/pk3lN-1fjQ 

Comment [14]
   See all comments [15]

Unsubscribe [16] to no longer receive posts from Hackaday.
Change your email settings at Manage Subscriptions [17]. 

TROUBLE CLICKING? Copy and paste this URL into your browser: 
http://hackaday.com/2018/03/02/new-part-day-atmegas-with-programmable-logic/


Thanks for flying with WordPress.com [18]

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VOX: 406-626-4304 

Links:
--
[1]
http://hackaday.com/2018/03/02/new-part-day-atmegas-with-programmable-logic/
[2] http://hackaday.com/author/brianbenchoff/
[3] http://www.microchip.com/wwwproducts/en/ATMEGA4809
[4] http://ww1.microchip.com/downloads/en/AppNotes/DS2451B.pdf
[5] http://hackaday.com/tag/atmega/
[6] http://hackaday.com/tag/atmega4809/
[7] http://hackaday.com/tag/ccl/
[8] http://hackaday.com/tag/configurable-custom-logic/
[9] http://hackaday.com/tag/lut/
[10] http://hackaday.com/tag/microchip/
[11] http://hackaday.com/tag/new-part-day/
[12] http://hackaday.com/category/hackaday-columns/
[13] http://hackaday.com/category/hardware/
[14]
http://hackaday.com/2018/03/02/new-part-day-atmegas-with-programmable-logic/#respond
[15]
http://hackaday.com/2018/03/02/new-part-day-atmegas-with-programmable-logic/#comments
[16]
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_

Re: [time-nuts] Time nut over from the old days

[djl]

Pete:  I need a handwarmer. We're having a colder than usual winter.
Don

On 2018-02-28 12:45, Pete Lancashire wrote:

If anyone wants it, he or she that comes up with the coolest reason can
have it. It rattles so I will take a look inside and post what I find

-pete

On Feb 28, 2018 10:54 AM, "John Franke"  wrote:

I still use them, both the Bliley and James Knights versions. 
Especially

like them for 100 KC crystals.

John Franke
WA4WDL

> On February 28, 2018 at 12:22 PM Pete Lancashire <
p...@petelancashire.com> wrote:
>
>
> https://photos.app.goo.gl/gIw4P1RQHPk2t4K33
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Re: [time-nuts] Teardown of Chinese made eBay GPS antenna.

[djl]

Fine. The Chinese have no concept of, or ignore, intellectual property 
rights. They will cheerfully use 13 year old girls to put together stuff 
using counterfeit parts and ripped circuits. There is little or no 
quality control. The problem is that these goods drive better goods out 
of the market.



On 2018-02-22 14:39, William H. Fite wrote:
I wish people would lighten up on Chinese goods. Perhaps you are not 
aware

that China builds for and sells to both the DOD and NASA. Chinese
manufacturers build to the specs they are given. You want cheap crap,
they'll build cheap crap. You want top quality, they'll build top 
quality.



On Thursday, February 22, 2018, Van Horn, David <
david.vanh...@backcountryaccess.com> wrote:

According to the data sheet, it looks pretty well in spec, and the 
part

has thermal shutdown.
http://ww1.microchip.com/downloads/en/DeviceDoc/mic5203.pdf

ESD hit maybe?
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Re: [time-nuts] Teardown of Chinese made eBay GPS antenna.

[djl]

 Chinese made, ... This
part looks almost identical to the Trimble Microcentered antenna I 
worked

on recently.


Right. It's Chinese made. 'nuff said.

Don

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Re: [time-nuts] Looking for some Frequency Electronics info....

[djl]

start with the power supplies, and go on until morning...
Don

On 2018-02-19 16:57, walter shawlee 2 wrote:

I recently got a strange little 1U FEI rack mounted unit called an
FE-7923F-100-1,
which appears to have rear 10MHz and dual 100Mhz outputs. it is called
a Frequency Reference Unit.

sadly, my unit has a fault light, and no outputs. All the internal
supplies look good, and there is an FE-83AA (10.0Mhz) and FE-1020-100
(100Mhz) OCXO inside.  both of these work (when measured at the
oscillators), and seem to have meaningful control including EFC, and I
tracked down the adjustments in a sea of what seem to be prototype
boards next to the oscillators. so, I have two good sources,
adjustable, but still no outputs.
the OCXO signals disappear into a set of boards with no useful
markings as to function, and look mainly digital.

the 100Mhz unit has only about 200mV p-p output, which seems low to
me, the other has lots of signal. I cannot find any data on either
unit on line or at the FEI website, so any data that is out there
would be very welcome, so I can be sure they at least are running
correctly.

I am hoping to use this rack as a source of RF reference signals in
other gear, but clearly I will have to either gut the rest of the
circuitry and add some new buffers, or figure out the rats nest of
hand wiring to determine why it's not working.  any help in that area
hugely appreciated, and I can send pics to anybody interested to know
more about the internals.

the rear apron has AC power in, a 10MHz output SMA, a switch next to
it that says INT/EXT REF. (set to INT), but no way to attach an
external ref.  then there's a D-Sub filtered connector, that runs to
the stacked digital boards, but its purpose is unknown as I cannot see
where the connections go.  there are also two 100Mhz SMA outputs, but
all outputs are dead, with no signal, and the front ONLINE green LED
is dark, and the red FAULT LED is lit. the oscillators do not run to
the rear jacks but disappear into three pcbs.

hoping for some FEI data if anybody has some to share.
all the best,
walter

--
Walter Shawlee 2, President
Sphere Research Corporation
3394 Sunnyside Rd.,  West Kelowna,  BC
V1Z 2V4  CANADA  Phone: (250) 769-1834
walt...@sphere.bc.ca
WS2: We're all in one boat, no matter how it looks to you.
Love is all you need. (John Lennon)
But, that doesn't mean other things don't come in handy. (WS2)

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Re: [time-nuts] Anyone have experience with this antenna?

[djl]

There's a picture of the guts in the ebay description...it's a dual 
patch antenna!

the patches seem to be trimmed to get a pattern.

On 2018-02-05 20:33, John Green wrote:

https://www.ebay.com/itm/High-Precision-L1-L2-GNSS-GPS-GLONASS-BeiDou-RTK-CORS-survey-antenna/162718512935?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

Listed on eBay as a L1/L2 antenna with decent specs. They seem to 
indicate
it is as good as a choke ring antenna. I suspect it is just a patch in 
a
fancy package. That is what the Leica and Trimble survey grade antennas 
I

have contain anyway. I bought one but haven't had the chance to do any
testing. I couldn't figure out how to get to the insides to take a peek
without damaging it. My antenna testing abilities are pretty feeble.
Mostly, I will just compare it to the Leica and Trimble to see how many
satellites it sees and look at position wander of the uBlox. Is there 
any

simple way to judge the quality of a GPS antenna?
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Re: [time-nuts] PBS, Tue evening, The Secret of Tuxedo Park

[djl]

pbs video player sucks big ones...

On 2018-01-16 18:47, Joseph Gray wrote:

If you want to watch this episode online, go here:
http://video.unctv.org/video/3008204310

This is the UNC Public TV web site.

Joe Gray
W5JG



On Tue, Jan 16, 2018 at 2:28 PM, Bill Tracey  wrote:


To record OTA television I use an HDHomeRun :
https://www.silicondust.com/hdhomerun/

I'll grab tonight's run of The Secret of Tuxedo Park

Cheers,

Bill

At 09:04 AM 1/16/2018, you wrote:

I can't stress enough how important Loomis was to the history of 
precise
timekeeping in early radio, telephone, pendulum clock, quartz 
oscillator
era. And for those of us who still have Loran-C receivers can thank 
him

(Loomis Radio Navigation -> LRN -> Loran).
.

If someone knows how to record any time/clock/navigation parts of PBS
show for non-US viewers let me know, off-list.

/tvb



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Re: [time-nuts] Allan variance by sine-wave fitting

[djl]

True that the models depend on the noise statistics to be iid, that is 
ergodic. That's the first assumption, and, while making the math 
tractable, is the worst assumption.

Don

On 2017-11-28 01:52, Mattia Rizzi wrote:

Hi


This is true. But then the Fourier transformation integrates time from

minus infinity to plus infinity. Which isn't exactly realistic either.

That's the theory. I am not arguing that it's realistic.


Ergodicity breaks because the noise process is not stationary.


I know but see the following.


Well, any measurement is an estimate.


It's not so simple. If you don't assume ergodicity, your spectrum 
analyzer

does not work, because:
1) The spectrum analyzer takes several snapshots of your realization to
estimate the PSD. If it's not stationary, the estimate does not 
converge.
2) It's just a single realization, therefore also a flat signal can be 
a
realization of 1/f flicker noise. Your measurement has *zero* 
statistical

significance.



2017-11-27 23:50 GMT+01:00 Attila Kinali :


Hoi Mattia,

On Mon, 27 Nov 2017 23:04:56 +0100
Mattia Rizzi  wrote:

> >To make the point a bit more clear. The above means that noise with
> > a PSD of the form 1/f^a for a>=1 (ie flicker phase, white frequency
> > and flicker frequency noise), the noise (aka random variable) is:
> > 1) Not independently distributed
> > 2) Not stationary
> > 3) Not ergodic
>
> I think you got too much in theory. If you follow striclty the statistics
> theory, you get nowhere.
> You can't even talk about 1/f PSD, because Fourier doesn't converge over
> infinite power signals.

This is true. But then the Fourier transformation integrates time from
minus infinity to plus infinity. Which isn't exactly realistic either.
The power in 1/f noise is actually limited by the age of the universe.
And quite strictly so. The power you have in 1/f is the same for every
decade in frequency (or time) you go. The age of the universe is about
1e10 years, that's roughly 3e17 seconds, ie 17 decades of possible 
noise.
If we assume something like a 1k carbon resistor you get something 
around
of 1e-17W/decade of noise power (guestimate, not an exact 
calculation).
That means that resistor, had it been around ever since the universe 
was

created, then it would have converted 17*1e-17 = 2e-16W of heat into
electrical energy, on average, over the whole liftime of the universe.
That's not much :-)

> In fact, you are not allowed to take a realization, make several fft and
> claim that that's the PSD of the process. But that's what the spectrum
> analyzer does, because it's not a multiverse instrument.

Well, any measurement is an estimate.

> Every experimentalist suppose ergodicity on this kind of noise, otherwise
> you get nowhere.

Err.. no. Even if you assume that the spectrum tops off at some very
low frequency and does not increase anymore, ie that there is a finite
limit to noise power, even then ergodicity is not given.
Ergodicity breaks because the noise process is not stationary.
And assuming so for any kind of 1/f noise would be wrong.


Attila Kinali
--
The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
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Re: [time-nuts] Allan variance by sine-wave fitting

[djl]

Forgot to add I think this can be proved mathematically. It's been a 
long time

Don

On 2017-11-22 12:52, djl wrote:

You have it right, Bob. fitting is essentially a narrow band filter
process.  Fitting thus has essentially the same errors.
Don

On 2017-11-22 09:19, Bob kb8tq wrote:

Hi

The “risk” with any fitting process is that it can act as a filter.
Fitting a single
sine wave “edge” to find a zero is not going to be much of a filter. 
It will not
impact 1 second ADEV much at all. Fitting every “edge” for the entire 
second

*will* act as a lowpass filter with a fairly low cutoff frequency.
That *will* impact
the ADEV.

Obviously there is a compromise that gets made in a practical 
measurement.
As the number of samples goes up, your fit gets better. At 80us you 
appear
to have a pretty good dataset. Working out just what the “filtering” 
impact

is at shorter tau is not a simple task.

Indeed this conversation has been going on for as long as anybody has 
been

presenting ADEV papers. I first ran into it in the early 1970’s. It is
at the heart
of recent work recommending a specific filtering process be used.

Bob


On Nov 22, 2017, at 10:58 AM, Ralph Devoe <rgde...@gmail.com> wrote:

Hi time nuts,
 I've been working on a simple, low-cost, direct-digital method 
for

measuring the Allan variance of frequency standards. It's based on a
Digilent oscilloscope (Analog Discovery, <$300) and uses a short 
Python
routine to get a resolution of 3 x 10(-13) in one second. This 
corresponds
to a noise level of 300 fs, one or two orders of magnitude better 
than a
typical counter. The details are in a paper submitted to the Review 
of

Scientific Instruments and posted at arXiv:1711.07917 .
 The method uses least-squares fitting of a sine wave to 
determine the

relative phase of the signal and reference. There is no zero-crossing
detector. It only works for sine waves and doesn't compute the phase 
noise

spectral density. I've enclosed a screen-shot of the Python output,
recording the frequency difference of two FTS-1050a standards at 1 
second
intervals. The second column gives the difference in milliHertz and 
one can
see that all the measurements are within about +/- 20 microHertz, or 
2 x

10(-12) of each other, with a sigma much less than this.
 It would interesting to compare this approach to other 
direct-digital

devices.

Ralph DeVoe
KM6IYN
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Re: [time-nuts] Allan variance by sine-wave fitting

[djl]

You have it right, Bob. fitting is essentially a narrow band filter 
process.  Fitting thus has essentially the same errors.

Don

On 2017-11-22 09:19, Bob kb8tq wrote:

Hi

The “risk” with any fitting process is that it can act as a filter.
Fitting a single
sine wave “edge” to find a zero is not going to be much of a filter. It 
will not
impact 1 second ADEV much at all. Fitting every “edge” for the entire 
second

*will* act as a lowpass filter with a fairly low cutoff frequency.
That *will* impact
the ADEV.

Obviously there is a compromise that gets made in a practical 
measurement.
As the number of samples goes up, your fit gets better. At 80us you 
appear
to have a pretty good dataset. Working out just what the “filtering” 
impact

is at shorter tau is not a simple task.

Indeed this conversation has been going on for as long as anybody has 
been

presenting ADEV papers. I first ran into it in the early 1970’s. It is
at the heart
of recent work recommending a specific filtering process be used.

Bob


On Nov 22, 2017, at 10:58 AM, Ralph Devoe  wrote:

Hi time nuts,
 I've been working on a simple, low-cost, direct-digital method 
for

measuring the Allan variance of frequency standards. It's based on a
Digilent oscilloscope (Analog Discovery, <$300) and uses a short 
Python
routine to get a resolution of 3 x 10(-13) in one second. This 
corresponds
to a noise level of 300 fs, one or two orders of magnitude better than 
a

typical counter. The details are in a paper submitted to the Review of
Scientific Instruments and posted at arXiv:1711.07917 .
 The method uses least-squares fitting of a sine wave to determine 
the

relative phase of the signal and reference. There is no zero-crossing
detector. It only works for sine waves and doesn't compute the phase 
noise

spectral density. I've enclosed a screen-shot of the Python output,
recording the frequency difference of two FTS-1050a standards at 1 
second
intervals. The second column gives the difference in milliHertz and 
one can
see that all the measurements are within about +/- 20 microHertz, or 2 
x

10(-12) of each other, with a sigma much less than this.
 It would interesting to compare this approach to other 
direct-digital

devices.

Ralph DeVoe
KM6IYN
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Re: [time-nuts] chrony vs ntpd

[djl]

Would a step recovery diode be better?
for example 
http://www.mwrf.com/analog-semiconductors/designing-step-recovery-diode-based-comb-generator

Don

On 2017-10-28 12:20, jimlux wrote:

On 10/28/17 10:34 AM, John Ackermann N8UR wrote:
Jim, I thought about using an RF-input sync pulse for alignment during 
the Solar Eclipse measurement experiment, but ended up running out of 
time to implement it.  But some very crude experiments indicated that 
it's not hard to generate an edge out of a PPS that creates a comb 
well past HF.  My idea was to do a divide-by-sixty to end up with 
pulse-per-minute rather than PPS.  The lower rate would be less 
annoying to filter out of the results.


I'm interested to hear if you end up doing this, and if so how.



Yes, a nice narrow pulse makes a nice comb.  I've done it for a single
shot wideband gain calibration across the band for my space HF
receiver (in ground test).

The tricky parts, I have found, are:
1) the rise and fall time have a big effect on the relative heights of
the comb vs freq - perfectly square gives you a nice sin(x)/x, but if
it starts to be not-square, then it rolls off faster.  I've been
thinking about how to do something that measures it

2) Amplitude of the pulse - that one seems pretty straightforward - a
good switch from a regulated voltage.

3) The effects of the antenna and receiver impedances - well - to a
certain extent, that's what I want to measure.   So the idea is that
if you inject a pulse through a known resistance into the
receiver/antenna combination (at the receiver input), and, I do this
at two or three different impedances, I should be able to back out the
impedance effects (with some TBD uncertainty).


So far, I've been experimenting with RF tone bursts from a 33622
function generator - Easy to detect, but I've not found a good way to
get a nice sharp marker - you can slide a matched filter along and get
a sort of pulse, but it's not what I want.

I'm starting to think that some sort of PN code might be the way to go
- It makes it easy to integrate over a longer time (e.g. many edges to
look at).





John


On 10/28/2017 12:04 PM, jimlux wrote:
Now that I have successfully connected my GPS receiver to my beagle 
and I'm getting pps ticks into the driver, etc. (thanks to info from 
several folks on this list!) the question arises of whether to use 
ntpd or chrony.


For my particular application, I'm more interested in synchronizing 
time on the local machine, not necessarily being a NTP server - all 
of my beagles have a GPS on them.  Of course, there may be times when 
a GPS doesn't work, or something else comes up where it would be 
useful for one of the machines to "get time" from somewhere else.


What I am doing is using the Beagle to capture RF samples (RTL-SDR) 
in a distributed array, with wireless connections among the nodes.  
The processing isn't necessarily real-time (maybe later..), for now, 
it's "trigger some seconds of capture at approximately the same time" 
and post process in matlab/octave.


There's all kinds of nondeterministic latency issues with the 
USB/RTL-SDR path, so I'm under no illusion that I can capture samples 
aligned to the 1pps.  However, what I *can* do is generate a "sync 
pulse" from the 1 pps and feed it into the RTL's RF input in some 
(TBD) way.
And the 1pps might give me a clever way to calibrate the frequency 
drift of the RTLSDR's clock.


Right now, I'm interested in HF signals (so the period is 30 ns at 
the top end, and 500 ns at the bottom end)




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Re: [time-nuts] Machining some aluminum help!

[djl]

Good even for mild steel too. Best is your good advice to use the drill 
press to keep the tap aligned.  softer aluminum alloys are very "sticky" 
and demand backing off a turn for almost every turn forward for cutting 
taps to break the chip. I've found that the 6/32 tap is the most easily 
broken. sigh.
Pay attention, the tap drill is not the same for the forming tap as it 
is for the cutting tap.

Don


On 2017-07-28 13:46, cdel...@juno.com wrote:

Well I did some research and found my new best friend!

If you remember I needed:  "I have a square aluminum tube 5" X 5" with 
a

.25" wall it's 8 1/2" long.

I need 20 holes in each end tapped for 4/40 and 1/2" deep."

This for a Rubidium standard I am working on.

I found all about self forming taps!

I drilled the 20 1/2" deep holes and then made a handwheel to attach to
the pulley on my drill press. After mounting the tap in the drill press
and putting a dab of Crisco on the tap I was able to tap each hole to a
depth of 7/16" as fast as I could turn the handwheel!

I then got another 8-32 self forming tap to do the holes for 15 
feedthru

capacitors, again as fast as I could turn the handwheel.

I'm very happy to discover these taps

Cheers,

Corby
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Re: [time-nuts] 5370B Input Board Repair [WAS: 5370B Question / help needed]

[djl]

Could it be that someone thought adhesive would be less prone to 
cracking from stress than solder?
Also, do you think that the adhesive could be cleaned one end at a time 
and replaced with solder?

I'm admittedly too lazy to look/try just now.
Don


On 2017-07-19 07:09, Gary Neilson wrote:

This is very interesting, I have a 5370B that has the same behavior as
yours. I will take the input board out again and give it a good
inspection. BTW, what did you use to clean the adhesive from the pads
?

Thanks
Gary

On 7/18/2017 2:41 AM, Thomas Allgeier wrote:

Hello All Again,



I’ve got my 5370B going now and in the process made a “discovery” 
which I thought might be worth sharing:


The A3 input board is a through-hole PCB with a few SMD capacitors and 
resistors on the reverse of the “switch area”. It turns out that on my 
5370 (2410A00777) these components are not soldered, but fitted with 
conductive adhesive. I first thought it was solder with a black 
coating but under a microscope it is clear that it is not solder at 
all. Most probably it is a mixture of epoxy and silver particles, or a 
similar compound. So no going over joints with a fine iron…


Inspecting all this carefully under the microscope I discovered that 
the “joints” on 2 resistors (R23 and R56) had cracked. As you know 
this board gets heat from the hybrid amplifier IC’s and due to the way 
the board is mounted to the front panel I guess it sees thermal 
stressing when the instrument warms up and cools down. While this 
obviously lasts a long time it looks that on my unit the adhesive has 
eventually cracked in places. (Vigorous switch activation and pressing 
/ pulling on the switch handles also won’t be helpful in this 
respect…) One of the resistors just fell off at the slightest touch 
with fine tweezers.




Anyhow, after removing the offending components, cleaning the pads of 
the adhesive, and soldering replacements in place, we have a perfect 
99.9x ns with the 10 MHz on the commoned inputs. Happy days!




So if any of your 5370’s have the kind of intermittent fault I 
described (and one or two other people seem to have reported) or 
instability that seems to originate from the A3 board – check the 
joints around the SMD’s.




I wonder why / how it ended up having the adhesive instead of solder – 
were earlier / later instruments the same, or was this a build change 
introduced at a certain period?




Hope the above is of help to somebody else,

Thomas.



Message: 1
Date: Sat, 15 Jul 2017 21:54:47 +0100
From: Thomas Allgeier 
To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] 5370B Question / help needed
Message-ID:

Re: [time-nuts] Yet Another GPSDO design - Timing on the move

[djl]

Thanks! for the nice reply. I did as you suggested and got a copy!
Don

On 2017-06-26 15:43, Jan-Derk Bakker wrote:

On Mon, Jun 26, 2017 at 10:43 PM, djl <d...@montana.com> wrote:


I'd really like to have a look at the schematic, but trying to read it
leads to some app requiring me to bare my machine's soul to an unknown 
app

developer. Could  plain .pdf be put somewhere not involving Google?



Save As... should hopefully fix that for now. My last Ubuntu upgrade 
killed
my server's Apache installation (presumably over an incompatibility in 
the
config files which I've not updated in the last decade). I hope to fix 
that
this week, so I can give a more proper home to the design (+ some 
pictures

+ some logs).

JDB.
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Re: [time-nuts] Yet Another GPSDO design - Timing on the move

[djl]

d'oh never mind
don

On 2017-06-26 14:43, djl wrote:

I'd really like to have a look at the schematic, but trying to read it
leads to some app requiring me to bare my machine's soul to an unknown
app developer. Could  plain .pdf be put somewhere not involving
Google?
Thanks
don

On 2017-06-26 14:17, William H. Fite wrote:

On Monday, June 26, 2017, Tom Van Baak <t...@leapsecond.com> wrote:



Be careful about that. Act like there are no outliers: every point is
trying to tell you something.



ARG! Your resident statistician just had a sudden, stabbing 
pain in

the head. Before an audience of statisticians, you would find that
statement extremely difficult to justify. Indeed, some would say it is
inherently self-contradictory.

Perhaps in this context it does not matter. Your knowledge is vastly
greater than mine in the TF domain.




/tvb

- Original Message -
From: "Jan-Derk Bakker" <jdbak...@gmail.com <javascript:;>>
To: <time-nuts@febo.com <javascript:;>>
Sent: Monday, June 19, 2017 3:44 PM
Subject: [time-nuts] Yet Another GPSDO design - Timing on the move


> Dear all,
>
> After a hiatus of seven years I have finished the first version of my
GPSDO
> design. The full schematic can be found at
https://drive.google.com/file/d/
> 0B7mNymXfcKMqaFcyRXdURC1KMXM/view?usp=sharing (Google Drive seems to
guess
> the file type wrong; Acrobat opens the file just fine). Its first use
will
> be in the telemetry system of my students' solar-powered boat (
> http://cleanmobility.info/voertuigen/solar-2015/ ), on a trip from
> Amsterdam to Monaco.
>
> The design objectives are, in decreasing order of importance:
>
> 1) Providing a reference frequency for a SDR system in the 868MHz ISM
band,
> having a frequency drift over a day no worse than 10% of the maximum
> Doppler shift at a relative speed of 100km/h, while consuming at most 2W
in
> steady-state from a 24V net
>
> 2) Testing/teaching platform for the evaluation of different design
choices
> in a GPSDO, including alternative phase detectors, EFC generation by DAC
vs
> PWM, FLL/PLL algorithms, timing vs navigation receivers, and OCXO choices
>
> 3) When equipped with a timing receiver, having ADEV/MDEV at most 10x
worse
> than a Thunderbolt in the interval between 1s and 1d.
>
> (Yes, objective 1 could be met with a quality OCXO, but where's the fun
in
> that?)
>
> Where possible I tried to stick to the suggested design criteria listed
in
> https://www.febo.com/pipermail/time-nuts/2007-April/025597.html .
>
> The primary phase detector is a TDC7200, which almost feels like cheating
> after all the trouble I went through last time (
> https://www.febo.com/pipermail/time-nuts/2010-August/049347.html ). The
> '7200 is used in Mode I, which needs at least 12ns between START and
STOP.
> A fairly vanilla synchronizer handles this. As I expect the phase offset
in
> lock to be zero (modulo hanging bridges), the first flip-flop is clocked
> with an inverted copy of the main clock to further reduce the possibility
> for metastability. U16/U17 latch the lower bits of clock divider U19/U18
to
> get around synchronizer uncertainty in the microcontroller. A second
> TDC7200 channel is added to ease comparison with other references or
> timestamp external events. (I have a mains ZCD in the works just for
this).
> Both channels have a simple flip-flop as an alternate phase detector; the
> second channel can be wired to be driven by the GPS PPS as well.
>
> The microcontroller board holds a 32MHz ATXMega256A3U. While this board
> cannot use the 10MHz oscillator for its main clock, both 10MHz and PPS
> inputs are available as event channels. The microcontroller board also
has
> a microSD socket for standalone phase data logging and a charger for a
> small LiIon cell that can provide power when the boat's systems are
powered
> down. U21 is a 128KB SRAM chip for scratch space, U13 is a FeRAM chip to
> store EFC settings (as EEPROM would wear out too fast with regular
writes,
> and I cannot guarantee having enough energy after detecting a brownout to
> only write to EEPROM in such conditions). The other systems for the boat
> already include a GPS module (Venus 6) which is used for PPS in normal
> circumstances; a footprint for a small Venus8-board offers an alternative
> in standalone use ( until I can get my hands on a 3v3 timing receiver ).
> The microcontroller measures system temperature, OCXO current and the
> voltages on the raw power nets.
>
> The EFC is based on a pair of 16-bit DACs plus a 24-bit ADC in a PID
loop,
> inspired by Linear/Jim Williams' AN86 ( http://www.linear.com/docs/4177
).
> The DACs are fairly noisy, an RC with a few film caps plus a quiet
follower
> should take care of that. Plan B for the EFC is a pair of 

Re: [time-nuts] Yet Another GPSDO design - Timing on the move

[djl]

I'd really like to have a look at the schematic, but trying to read it 
leads to some app requiring me to bare my machine's soul to an unknown 
app developer. Could  plain .pdf be put somewhere not involving Google?

Thanks
don

On 2017-06-26 14:17, William H. Fite wrote:

On Monday, June 26, 2017, Tom Van Baak  wrote:



Be careful about that. Act like there are no outliers: every point is
trying to tell you something.



ARG! Your resident statistician just had a sudden, stabbing 
pain in

the head. Before an audience of statisticians, you would find that
statement extremely difficult to justify. Indeed, some would say it is
inherently self-contradictory.

Perhaps in this context it does not matter. Your knowledge is vastly
greater than mine in the TF domain.




/tvb

- Original Message -
From: "Jan-Derk Bakker" >
To: >
Sent: Monday, June 19, 2017 3:44 PM
Subject: [time-nuts] Yet Another GPSDO design - Timing on the move


> Dear all,
>
> After a hiatus of seven years I have finished the first version of my
GPSDO
> design. The full schematic can be found at
https://drive.google.com/file/d/
> 0B7mNymXfcKMqaFcyRXdURC1KMXM/view?usp=sharing (Google Drive seems to
guess
> the file type wrong; Acrobat opens the file just fine). Its first use
will
> be in the telemetry system of my students' solar-powered boat (
> http://cleanmobility.info/voertuigen/solar-2015/ ), on a trip from
> Amsterdam to Monaco.
>
> The design objectives are, in decreasing order of importance:
>
> 1) Providing a reference frequency for a SDR system in the 868MHz ISM
band,
> having a frequency drift over a day no worse than 10% of the maximum
> Doppler shift at a relative speed of 100km/h, while consuming at most 2W
in
> steady-state from a 24V net
>
> 2) Testing/teaching platform for the evaluation of different design
choices
> in a GPSDO, including alternative phase detectors, EFC generation by DAC
vs
> PWM, FLL/PLL algorithms, timing vs navigation receivers, and OCXO choices
>
> 3) When equipped with a timing receiver, having ADEV/MDEV at most 10x
worse
> than a Thunderbolt in the interval between 1s and 1d.
>
> (Yes, objective 1 could be met with a quality OCXO, but where's the fun
in
> that?)
>
> Where possible I tried to stick to the suggested design criteria listed
in
> https://www.febo.com/pipermail/time-nuts/2007-April/025597.html .
>
> The primary phase detector is a TDC7200, which almost feels like cheating
> after all the trouble I went through last time (
> https://www.febo.com/pipermail/time-nuts/2010-August/049347.html ). The
> '7200 is used in Mode I, which needs at least 12ns between START and
STOP.
> A fairly vanilla synchronizer handles this. As I expect the phase offset
in
> lock to be zero (modulo hanging bridges), the first flip-flop is clocked
> with an inverted copy of the main clock to further reduce the possibility
> for metastability. U16/U17 latch the lower bits of clock divider U19/U18
to
> get around synchronizer uncertainty in the microcontroller. A second
> TDC7200 channel is added to ease comparison with other references or
> timestamp external events. (I have a mains ZCD in the works just for
this).
> Both channels have a simple flip-flop as an alternate phase detector; the
> second channel can be wired to be driven by the GPS PPS as well.
>
> The microcontroller board holds a 32MHz ATXMega256A3U. While this board
> cannot use the 10MHz oscillator for its main clock, both 10MHz and PPS
> inputs are available as event channels. The microcontroller board also
has
> a microSD socket for standalone phase data logging and a charger for a
> small LiIon cell that can provide power when the boat's systems are
powered
> down. U21 is a 128KB SRAM chip for scratch space, U13 is a FeRAM chip to
> store EFC settings (as EEPROM would wear out too fast with regular
writes,
> and I cannot guarantee having enough energy after detecting a brownout to
> only write to EEPROM in such conditions). The other systems for the boat
> already include a GPS module (Venus 6) which is used for PPS in normal
> circumstances; a footprint for a small Venus8-board offers an alternative
> in standalone use ( until I can get my hands on a 3v3 timing receiver ).
> The microcontroller measures system temperature, OCXO current and the
> voltages on the raw power nets.
>
> The EFC is based on a pair of 16-bit DACs plus a 24-bit ADC in a PID
loop,
> inspired by Linear/Jim Williams' AN86 ( http://www.linear.com/docs/4177
).
> The DACs are fairly noisy, an RC with a few film caps plus a quiet
follower
> should take care of that. Plan B for the EFC is a pair of PWM outputs
from
> the microcontroller followed by a 4-pole filter. Both 1in2 OCXOs with and
> without internal reference can be used, as well as cheaper
Connor-Winfield
> DOC/DOT-series XOs.
>
> What else? Status LEDs, a heavily filtered synchronized switch-mode
supply
> (necessary to 

Re: [time-nuts] Two pieces of old General Radio Freq. Nuts

[djl]

Yep, GR once made the best. The GR connector had at least three things 
going; as noted hermaphroditic. No need for several sexes. Second, they 
are seamless 50 ohms, very very small reflections at the connection. 
Third, banana plugs (also a GR idea, I think) fit in the center "post" 
of the connector without wrecking anything. GR also made an 
hermaphroditic connector good to several GHz before passing into legend. 
. .

Don


On 2017-05-27 05:01, Bob kb8tq wrote:

Hi

On May 26, 2017, at 11:21 PM, Gary Woods  
wrote:


On Mon, 22 May 2017 05:59:59 -0700, you wrote:


https://goo.gl/photos/tygN5ZFeFLUhc4zX6

Near Portland Oregon


Neat stuff...did anybody but GR use those hermaphrodite connectors?


At one time, GR was pretty much the only source for a wide range of RF
and microwave test gear. Anything that was going to work with that gear
may have come with the GR connectors. That includes stuff like 
attenuators,
cables, and other bits of “lab clutter”. When you checked the box for 
the

GR connectors, the price went up quite a bit. That made the gizmos with
the connectors on them a bit more rare than they otherwise would be.

Bob



I have
an adapter for them that came with a wide-band amplifier; "delay line"
type, with a whole row of, I think, 6AK5s in it.


--
Gary Woods AKA K2AHC- PGP key on request, or at 
home.earthlink.net/~garygarlic

Zone 5/4 in upstate New York, 1420' elevation. NY WO G

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Re: [time-nuts] The Witching Hour; short fiction that will likely amuse time-nuts

[djl]

But what if Tal Avda is in Arizona

On 2017-05-21 14:50, Gregory Maxwell wrote:

Found on the web:

http://slatestarcodex.com/2013/11/03/the-witching-hour/
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Re: [time-nuts] A good GPS-Receiver with 1PPS output...

[djl]

Can't find this on Tindie???

On 2017-05-10 09:03, Mark Sims wrote:

The GPS with the lowest PPS jitter/sawtooth is the Venus timing
receiver... around 6 ns.   Nick Sayer sells one on Tindie for $50.  It
is mounted on a board that has the same pinouts as the Adafruit
Ultimate GPS.  Also Navspark sells one for more $.

Lady Heather talks to the Venus receivers.
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[time-nuts] odd frequencies

[djl]

Hi: Ran across this recently, for those looking for odd stable 
frequencies.

http://www.qrp-labs.com/ocxokit
I haven't built one of these, but for $16 plus shipping, hey.
It does use a single-loop oven, built in.
I've had conversation with QRP labs, and found them knowledgeable and 
congenial.
Toyed with ordering one for testing, but haven't done so yet. The pile 
is already high.
Certainly can get frequencies out with low-end OCXO stability at a very 
reasonable price if indeed it works.

Don

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Re: [time-nuts] Vintage Frequency Measurement

[djl]

The BC-221 was the backbone of WW2 communications. How else were all 
those sloppy BC-348's and AR-13's set to the called-for frequencies?  
Same for shipboard.

Don


On 2017-02-13 13:05, Brooke Clarke wrote:

Hi Bob:

The BC-221 is usually referred to as either a Frequency Meter or a
Heterodyne Frequency Meter.

--
Have Fun,

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

 Original Message 

Hi

Ok, so how does that make a BC-221 a wave meter?

Bob


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Re: [time-nuts] OT: Eagle PC CAD now Autodesk, $500/year

[djl]

bought any prescription drugs lately?

On 2017-01-20 09:58, Bob Camp wrote:

Hi

I completely agree that their spin at acquisition and the reality of
what just came out
is completely amazing. They said they would never do this and that.
What they are doing
is exactly what they said they would not do.

It’s a rare board that I do in < 4 layers. It’s also quite normal to
have designs above
160 CM^2. If I have 4 layers, there *will* be signals on all those
layers. That puts me
squarely in the $500 / yr subscription. A month ago that put me in a
perpetual license
that I paid < 1/2 that for.

It is not just that the cost has gone up. A number of license
“categories” have vanished.
The free version is still there, and just as useless for what I do.
That’s about the only
one that is rational at this point.

So yes, I’m at least as bothered by this as anybody else. What I would
suggest is to
take a deep breath, sit back, yell at them a bit (along with everybody
else that has
a license) and see what they do. It is abundantly clear that they have
a major disconnect
between this and what they have said. There is a lot of explaining for
them to do. Part of that
could easily be another couple license categories. I’m certainly in no
hurry to switch
packages.

Right now Fusion 360 is something I use a LOT  more than I use Eagle.
This week (month .. year)
it is free for me to do that. Why is Fusion free to a basement guy and
Eagle pay?
That’s not at all clear. Fusion is buggy as can be. Eagle needs some
updates. Both
have a lot of development $$$ that they will be sucking up. Yes that
has to get paid
for. It’s not clear that a revenue stream based on hobbyists paying 
$500 a year

is rational. My guess is Autodesk will figure that out. They may
abandon the whole
basement thing, they may not …. we’ll see.

Bob


On Jan 19, 2017, at 10:52 PM, Richard (Rick) Karlquist 
 wrote:


Off topic, but probably a lot of disgrunted Eagle users on this list.
Its official, you will now have to pay $500 per year for a
professional license from Autodesk.  The spin meistering of the
announcement would make George Orwell proud.  I don't see any way they
can keep me from just using the license I currently own, at least
on the OS's it supports.  (Parenthetically, like many users, I
am also digging in my heels in terms of staying at Windows 7).

Still, the question arises:  are there any affordable alternatives?
Don't have to be entirely free.  I am looking for any trends out
there as to what tool will attract a critical mass of users in
the future.  There is strength in numbers.

Comments?

Rick N6RK
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Re: [time-nuts] quartz drift rates, linear or log

[djl]

Interesting, Tom. I don't think I see any of those pesky grain boundary 
shifts or readjustments in the lattice structure? If I remember, these 
can cause instant shifts in frequency that do not heal?

Don


On 2016-11-12 14:54, Tom Van Baak wrote:

There were postings recently about OCXO ageing, or drift rates.

I've been testing a batch of TBolts for a couple of months and it
provides an interesting set of data from which to make visual answers
to recent questions. Here are three plots.


1) attached plot: TBolt-10day-fit0-e09.gif (
http://leapsecond.com/pages/tbolt/TBolt-10day-fit0-e09.gif )

A bunch of oscillators are measured with a 20-channel system. Each
frequency plot is a free-running TBolt (no GPS, no disciplining). The
X-scale is 10 days and the Y-scale is 1 ppb, or 1e-9 per Y-division.
What you see at this scale is that all the OCXO are quite stable.
Also, some of them show drift.

For example, the OCXO frequency in channel 14 changes by 2e-9 in 10
days for a drift rate of 2e-10/day. It looks large in this plot but
its well under the typical spec, such as 5e-10/day for a 10811A. We
see a variety of drift rates, including some that appear to be zero:
flat line. At this scale, CH13, for example, seems to have no drift.

But the drift, when present, appears quite linear. So there are two
things to do. Zoom in and zoom out.


2) attached plot: TBolt-10day-fit0-e10.gif (
http://leapsecond.com/pages/tbolt/TBolt-10day-fit0-e10.gif )

Here we zoom in by changing the Y-scale to 1e-10 per division. The
X-scale is still 10 days. Now we can see the drift much better. Also
at this level we can see instability of each OCXO (or the lab
environment). At this scale, channels CH10 and CH14 are "off the
chart". An OCXO like the one in CH01 climbs by 2e-10 over 10 days for
a drift rate of 2e-11/day. This is 25x better than the 10811A spec.
CH13, mentioned above, is not zero drift after all, but its drift rate
is even lower, close to 1e-11/day.

For some oscillators the wiggles in the data (frequency instability)
are large enough that the drift rate is not clearly measurable.

The 10-day plots suggests you would not want to try to measure drift
rate based on just one day of data.

The plots also suggest that drift rate is not a hard constant. Look at
any of the 20 10-day plots. Your eye will tell you that the daily
drift rate can change significantly from day to day to day.

The plots show that an OCXO doesn't necessarily follow strict rules.
In a sense they each have their own personality. So one needs to be
very careful about algorithms that assume any sort of constant or
consistent behavior.


3) attached plot: TBolt-100day-fit0-e08.gif (
http://leapsecond.com/pages/tbolt/TBolt-100day-fit0-e08.gif )

Here we look at 100 days of data instead of just 10 days. To fit, the
Y-scale is now 1e-8 per division. Once a month I created a temporary
thermal event in the lab (the little "speed bumps") which we will
ignore for now.

At this long-term scale, OCXO in CH09 has textbook logarithmic drift.
Also CH14 and CH16. In fact over 100 days most of them are logarithmic
but the coefficients vary considerably so it's hard to see this at a
common scale. Note also the logarithmic curve is vastly more apparent
in the first few days or weeks of operation, but I don't have that
data.

In general, any exponential or log or parabolic or circular curve
looks linear if you're looking close enough. A straight highway may
look linear but the equator is circular. So most OCXO drift (age) with
a logarithmic curve and this is visible over long enough measurements.
But for shorter time spans it will appear linear. Or, more likely,
internal and external stability issues will dominate and this spoils
any linear vs. log discussion.

So is it linear or log? The answer is it depends. Now I sound like Bob 
;-)


/tvb

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Re: [time-nuts] HP 5275A

[djl]

Just homemade opto-isolators. Used in choppers, too. The transistor was 
indeed bonded to the heatsink.  Just replace the whole thing with a 
3-legged regulator? or simply a modern PNP t0-220 with a little heat 
sink on it.

73, Don


On 2016-11-06 15:15, paul swed wrote:
Don't know what to say on the transistor. It may have been actually 
made

that way. They did lots of things back then. Yes familiar with the bcd
decoder its used in the 5245 class counters also. I think someone was 
doing
some funny stuff at lunch time to come up with that. It was the 60's 
after

all.
How about some pix of a 9815 calc. That would be pretty neat.
On really old stuff if you can't find the part needed its pretty easy 
to
replace the whole function with modern answers. I know it sort of 
breaks

the original mode but for me at least its a case of getting it going.
Regards
Paul
WB8TSL

On Sun, Nov 6, 2016 at 1:59 PM, Adrian Godwin  
wrote:


Slightly off-topic, as this is a general repair question. But it's a 
TIC.


I'm repairing a 5275A timer (all-discreet count logic to 100MHz, neon 
bulb
display, a most amazing bcd to decimal decoder made from neons and 
LDRs,
1-2-2-4 decade counters ..) and the current problem is a 2n1038-2 
germanium

T05 transistor in the power supply.

It's mounted in an aluminium bush which is then isolated from the 
chassis.
I don't think the bush is also a collet but I can't see how to remove 
the
transistor. It resists ungentle pushing .. should I push it with a 
hammer ?

Or is there a kinder way ?

(I'm hoping to eventually put this into a system with a 101A 
oscillator and
a 9815A calculator to measure the ADEV of a Boule electric pendulum 
clock).

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Re: [time-nuts] So what’s inside that Cs Beam Tube anyway?

[djl]

Echo, Magnus. Thanks, Skip!  Easy now to see the incredible expense of 
building one of these! Kinda Kludgy; Love the s/s spot welded keepers on 
the screw heads, e.g.
My really dumb question is, why isn't there Cs plated on everything? Or 
is the Cs contained in the rf cavity only? I think I see a window on one 
end...

Thanks again, Don

On 2016-10-31 15:20, Magnus Danielson wrote:

Hi Skip,

Many thanks for taking the effort and describing what we see.
Good thing to tinker around with, if you have one. Good conversation 
piece. :)


Cheers,
Magnus

On 10/31/2016 09:54 PM, Skip Withrow wrote:

Hello Time-Nuts,



I recently acquired a stock of dead cesium beam tubes, and my 
curiosity got
the best of me, so I have cut one open.  After watching lots of 
YouTube
video of burning and exploding cesium I was a little leery at first. 
The
first step was to make a very small hole just to let a small amount of 
air
in, no flames or heat so I let it sit for a while for any reactions 
with
air to take their course.  Next I proceeded to cut off the ends, and 
after

that the bottom of the unit, finally I trimmed the top off as far as I
could.  Pictures are linked below for your enjoyment.  I have attached 
two

of the before and after at low resolution.



1. http://www.rdrelectronics.com/skip/CS-tube/cstube1.jpg



This is the before picture of a tube (not the actual one opened).  It 
is HP
part number 05061-6077.  The band around the center of the tube is a 
mu

metal shield that is removed by removing the screws along the seam.
Unfortunately
11 of the 14 tubes that I received had the cables cut as shown 
(ouch!).




2. http://www.rdrelectronics.com/skip/CS-tube/cstube2.jpg



This is a shot of the deconstructed tube.  The cesium oven is on the 
left,

the microwave cavity is in the center (under a metal cover), and the
detector is on the right.



3. http://www.rdrelectronics.com/skip/CS-tube/cstube3.jpg



This is the oven end of the tube.  The oven (with the cesium) is the 
copper
vessel.  The ion trap assembly is at the top (with magnet).  The first 
beam
magnet is between the oven and the microwave cavity.  One thing that I 
can
say is that HP brought the art of spot welding to a new level.  Note 
the

stainless steel strips welded over the screw heads (and lots of other
things).



4. http://www.rdrelectronics.com/skip/CS-tube/cstube4.jpg



This is the detector end of the tube.  I believe the hot wire ionizer 
is
the broken metal strip.  The electron multiplier/detector is in the 
metal
box above it.  The second beam magnet sits between the microwave 
cavity and

the electronics at this end of the tube.  I don’t think I broke the
filament, this was probably the failure mode of this tube.  Also note 
that

all the wiring insulation is ceramic tubing, since insulation that out
gasses in vacuum is a no-no.



5. http://www.rdrelectronics.com/skip/CS-tube/cstube5.jpg



This is the bottom view of the tube for completeness.  I have not yet
removed the cover that is over the microwave cavity (and has the 
C-field

coil around it).



6. http://www.rdrelectronics.com/skip/CS-tube/cstube6.jpg



This is the top of the tube with the potting compound removed.  I was
surprised to find a couple of embedded resistors.  I guess the good 
news is
that it would be easy enough to remove the potting and solder on new 
wires

if deemed useful.



7. http://www.rdrelectronics.com/skip/CS-tube/cstube7.jpg



This is just a close-up of the broken hot wire ionizer (and all the 
spot

welds).



8. http://www.rdrelectronics.com/skip/CS-tube/cstube8.jpg



This is a close-up of the ion trap where the +3500V connects.  I’m not 
a
physics expert, but didn’t think about a magnet being involved.  I 
don’t

think any of the drawings that I have seen have ever mentioned it.



So, enjoy.  I will most likely be throwing the rest of the tubes up on 
ebay
at some point.  If there is strong interest in having them cut open 
first
please let me know.  I intend to cut up some wood to make an 
appropriate

stand and add this one to my tube collection.



Sorry for the long post, but I hope you found it informative.

Regards,

Skip Withrow



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Re: [time-nuts] New PPB rated TCXO

[djl]

But how the heck did they get some? According to the website, even data 
sheets are not available.

Don

On 2016-10-10 21:32, Henry Hallam wrote:

I can attest that that oscillator was a lifesaver recently in a
project I was tangentially involved with.  They had tried several
TCXOs and were plagued with thermal and vibration sensitivity.  They
dropped in the SiTime and it worked like a charm.

Henry

On Mon, Oct 10, 2016 at 7:02 PM, Nick Sayer via time-nuts
 wrote:
The video linked on that page is particularly interesting (if you take 
it on face value that they're not faking it. ;) ).


Sent from my iPhone

On Oct 10, 2016, at 8:03 AM, Robert LaJeunesse  
wrote:


For general group information, as SiTime datasheet is not open to the 
public (yet?).


https://www.sitime.com/products/precision-super-tcxo

Actually a MEMS oscillator, comparison video against quartz TCXO is 
interesting.


Claimed Key Features:
- 30x better dynamic performance for macro cells, small cells, syncE 
and optical networks

- 3e-11 Allan Deviation (ADEV)
- 0.2 ps/mv PSNR, eliminating dedicated LDO
- No activity dips or microjumps
- 10x better dynamic stability, replacing OCXOs in IEEE 1588 
applications

- 1 to 5 ppb/°C frequency over temperature slope
- -40°C to +105°C operation uniquely enables fan-less outdoor 
equipment
- 20x greater vibration resistance ensures continuous system 
operation


Frequency range 1MHz to 220MHz (via 2 product types) so some form of 
synthesizer/divider is inherent.


Bob L.
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Re: [time-nuts] New PPB rated TCXO

[djl]

Looks promising, but with no data sheets and no purchase source or 
pricing, just more vaporware...

Don

On 2016-10-10 20:02, Nick Sayer via time-nuts wrote:

The video linked on that page is particularly interesting (if you take
it on face value that they're not faking it. ;) ).

Sent from my iPhone

On Oct 10, 2016, at 8:03 AM, Robert LaJeunesse  
wrote:


For general group information, as SiTime datasheet is not open to the 
public (yet?).


https://www.sitime.com/products/precision-super-tcxo

Actually a MEMS oscillator, comparison video against quartz TCXO is 
interesting.


Claimed Key Features:
- 30x better dynamic performance for macro cells, small cells, syncE 
and optical networks

- 3e-11 Allan Deviation (ADEV)
- 0.2 ps/mv PSNR, eliminating dedicated LDO
- No activity dips or microjumps
- 10x better dynamic stability, replacing OCXOs in IEEE 1588 
applications

- 1 to 5 ppb/°C frequency over temperature slope
- -40°C to +105°C operation uniquely enables fan-less outdoor 
equipment

- 20x greater vibration resistance ensures continuous system operation

Frequency range 1MHz to 220MHz (via 2 product types) so some form of 
synthesizer/divider is inherent.


Bob L.
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Re: [time-nuts] HP 59309A Clock runs, sets via GPIB, but no GPIB output?

[djl]

Hi Bob et al:
I have 4 of these, got some time ago.  Here is the data from the ROM's:
s/nRom no
2510A04059   hp1818-2295A  2335
2136A03167   hp1818-2295A  0844  this one white ceramic with lotsa 
gold; the eldest.
2702A04579$M$hp1818-2295A  2912  this one costcutting. boards 
cheaper, no instructions on the bottom cover.

2510A04243   hp1818-2295A  2390

Hope this is of some interest.  I also modified a couple of them by 
using some spare buffers, U7 on the middle board to TP1, and ran the 
output to the extremely convenient BNC for external power; the buffer 
chip is right next to it!  So I have a very convenient 1 pps. Note you 
can choose the external freq standard to be 1, 5, or 10 MHz with an 
internal switch by the battery holder. I don't use an internal 9v 
battery with these, it does not keep the readouts alive, just keeps the 
internal osc and chain going.
I've never played with the GPIB, mainly because AFIRC, it only reads out 
to the second.

Don


On 2016-10-09 19:48, Bob wrote:

Hi Tom & Paul,

Some progress with the HP 59309A clock debug.  Built a ROM reader
(Teensy++, a 28 pin WW socket, jumpers) and read out the HP 59309A U2
ROM.

Compared the user manual to my readings, found three stuck output bits
out of sixteen, and another few dozen assorted differences out of the
4096 ROM bits.

Also, while moving U2 to the reader socket I noticed that the chip is
stamped 1818-2295A 2335 vs. the schematic which states U2 is a
1818-2193.  Perhaps the U2 state machine was updated?

The O1 (part of Next Address) bit, O9 (LOAD) bit and O11 (Rout) bit
always read 0.  Together those stuck-at-0 bits compose the vast
majority of the bit differences.  LOAD being always zero explains why
I don't see data written into the RAM when watching with a logic
analyzer.

I'm 99% sure there is at least some bit rot, in particular there is a
long unused block at the end of the Talk Enable = 1 table, where all
addresses should match, and in the middle of that range there are just
a few wrong bits.

A small number of differences exist in other Next Address and Next
Qualifier columns, but there are only a few, not easy to tell if they
are just changes to the state machine or more bit rot.

Digging further, the serial number prefix 2510A is much newer than the
1632A prefix mentioned in the manual I'm looking at, so there could be
differences in the schematic.  Not clear if HP change pages up to
2510A exist, I've not found them so far.

At this point, I can think of a few paths to take...

a) Leave it alone, still works fine as a desk clock, but useless for
reading TOD via HP-IB.

b) Build a little adapter board and replace U2 with a self-programmed
16 bit EPROM or a pair of 8 bit EPROMs.  I could use the code in the
manual, buzz out the circuit to validate the schematic, and (if
needed) reverse engineer the state machine.

Tom and/or Paul, would you consider lifting the cover off your clock
(just 2 screws in the back) and peeking at the part number on your U2
chips?  That's the 28 pin ceramic ROM in the socket on the A5 board
which is the one at the far left looking from the front.  The ROM is
at the top of the board and should be visible without touching
anything.

If someone happens to have a ROM stamped 1818-2295A 2335, it would of
course be great to capture the bits, to remove the remaining guesswork
in creating a replacement image.  Naturally, I checked the ROMs on
Didier's site, but didn't see any for the 59309A.

In conclusion, reading the U2 ROM shows three stuck bits, including
LOAD, which explains what I saw on the logic analyzer.

Cheers,

Bob


On Oct 7, 2016, at 5:15 PM, Tom Van Baak  wrote:

Hi Bob,

Yes, the hp 59309A is a wonderful little LED clock. I just re-tested 
the program I wrote to read/write the time and it still works.


For others that are wondering, the code is at 
http://leapsecond.com/tools/hp59309.c and a Win32 exe is there too.


Anyway, one possible suggestion is for you to use ++read 10 instead of 
just ++read. The 59309A is an early byte-oriented HP-IB device and the 
Prologix command set is more meant for line oriented communication 
(using CR or LF or EOI for termination). So when I use ++read10 
everything is fine, but ++read, or ++read9 or ++read11 or ++read 
anything else will cause the Prologix to go into an infinite loop.


One other idea that may shed light on your problem is to use the /d 
(debug) option and have a look at the exact communication between the 
program and the Prologix and the 59309A. Then do the same with your 
Python code to see if it matches, down to the byte. Again, these 
vintage HP-IB instruments are wonderfully simple but they don't always 
take well to things we take for granted these days like extraneous 
line terminators or spaces or open-ended reads and such. If you really 
want some fun, use a GPIB bus analyzer.


Attached is the debug log from my 59309A.

If all else fails I can send you a known 

Re: [time-nuts] TimeLab

[djl]

That's easy, Magnus. Do not use a Fluke counter :-)
Don

On 2016-10-09 13:02, KA2WEU--- via time-nuts wrote:

You guys never give up, happy Sunday


In a message dated 10/9/2016 2:46:02 P.M. Eastern Daylight Time,
mag...@rubidium.se writes:

Hi,

Agree. However, one need to make sure that the counter  triggering 
never

flukes a measurement.

There is a few things  missing to make it work much much better.

Cheers,
Magnus

On  10/09/2016 08:35 PM, Bob Camp wrote:

Hi

I understand  the “keep it simple” concept, even if I rarely practice 
it

:)


 I would indeed like to get time tagging of phase measurements better

integrated with some of these
tools. The whole “was that a dropout in  the signal or a counter 
issue”

thing is rarely handled in a
very good  fashion. It also just happens to be a pretty good addition 
to

a comb  measurement system

as well.

 Bob



On Oct 9, 2016, at 1:33 PM, Magnus Danielson

 wrote:


Hi  Bob,

There is so many things that could be done  differently if we started
with a clean sheet. I was intentionally not going  down that road but 
more

thinking about practical setups with the stuff we  have, or very small
additions.


Cheers,
 Magnus

On 10/09/2016 07:26 PM, Bob Camp  wrote:

Hi



 On Oct 9, 2016, at 1:22 PM, Magnus Danielson

  wrote:


Hi Bob and  Bob,

This is why the two-counter setup  is so messy, you have to have
software that will sync up and query them  alternatively. You also need 
to make

sure you get the counters to trigger.  Besides, another issue is that
difference in the two counters read-outs will  cause a false signal,
so calibration
and compensation becomes important to  remove that.


That’s why I believe the time  tagger + counter is the better 
solution
rather than multiple counters. Let it  give you the global information 
and
then use it to sort out what you see from  the counter. Yes, a full 
blown
multi channel time tagger with picosecond  resolution would be better 
still.

That’s going to cost more than  $5….


 Bob



Using a picket  fence type of triggering approach is cheaper and
easier to maintain. Some mild  software support for the processing and 
it will
work like a charm. Calibration  for true zero offset is needed, but 
relatively

easy to implement, you want  that anyway.


 Cheers,
Magnus

On  10/09/2016 07:02 PM, Bob Stewart wrote:

Hi  Bob,
I had actually thought about making a server for  the Prologix
Ethernet adapters, but I gave up when I considered the issue of  two 
processes
trying to claim the same device.  I've experimented with  using a C 
program to
capture multiple GPIB ports to a live file.  But, I  can't figure out 
how to
get the "live" part to work when running Timelab on a  Windows client 
in a

Virtual Box under a Linux server that is collecting the  data.  I think
Santa may have to bring me another GPIB adapter this  Christmas.


 Bob
 -
 AE6RV.com

GFS GPSDO  list:
 groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp 
To:  Bob Stewart ; Discussion of precise time and

frequency  measurement 

Sent: Sunday,  October 9, 2016 11:50 AM
Subject: Re: [time-nuts]  TimeLab

 Hi

On Oct 9, 2016, at  12:27 PM, Bob Stewart   
wrote:


Hi  Bob,
Is it actually possible to address two  devices on one GPIB 
adapter
with Timelab?  I admit to not reading the  documentation carefully, but 
I've
not been able to do this directly.  The  only way I could think of 
doing it
was to use some software to send the data  to a file and then use 
Timelab
to pull the data from the file.  Maybe NI  software allows you to 
configure

this?


That was my poorly  stated point :) … you would have to add the

ability to identify and address  multiple devices.


 Bob



 Bob
 
-

 AE6RV.com

GFS GPSDO  list:
 groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp 
 To: Discussion of precise time and frequency measurement



Sent: Sunday, October  9, 2016 8:42 AM
Subject: Re: [time-nuts]  TimeLab

 Hi

Given that *some*  of us have more than errr … one counter  :)

There are several  setups that involve two or three counters to

resolve some of these issues.  Having
multiple serial ports or multiple devices  on a GPIB isn’t that 
big

a problem. Addressing multiple  devices
(setting up the addresses in TimeLab) is  an added step. Coming 
up

with standard setups would be  the
first step. Getting them documented to the  degree that they 
could

be run without a lot of hassle would  be

the next  step.

Another fairly  simple addition (rather than a full blown 
counter)

would be some sort of MCU  to time tag
the input(s). It’s a function that is  well within the 
capabilities

of a multitude of cheap demo cards. Rather  than

defining a specific 

[time-nuts] cleanup

[djl]

Clearing and cleaning. Have stuff fs, pickup, very cheap. 5370a's 5370b, 
3-5320A all with precision osc's 3325a fcn gen, Kode 3100, all working 
5335a counts 1/2, plain xtal, and two J Seamon beaglebones for 5370's, 
unused. BB's are not for sale separately. Pick it all up here,I'm only 2 
mi of good road off I90. Contact me off list at djl ampersand montana 
dot com. There is more stuff here as well. Big sale.

Thanks for your patience.
Don

--
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PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304

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Re: [time-nuts] Quartz Crystal Motional Movement

[djl]

excellent vid, Bryan!

On 2016-06-25 03:48, Bryan _ wrote:

Quartz Crystal motional movement...
https://youtu.be/y-rCgumTn4Q
-=Bryan=-


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Re: [time-nuts] Commercial software defined radio for clock metrology

[djl]

This might be a good job for the Red Pitaya q.v.
Don


On 2016-05-27 18:17, Bruce Griffiths wrote:

On Thursday, May 26, 2016 06:40:26 PM Bob Camp wrote:

Hi

Very interesting paper, thanks for sharing !!

One question:

In many DMTD (and single mixer) systems, a lowpass and high pass 
filter are
applied to the signal coming out of the mixer. This is done to improve 
the
zero crossing detection. It also effectively reduces the “pre 
detection”
bandwidth. My understanding of the setup in your paper does not do 
this
sort of filtering. It simply operated directly on the downconverter 
signal.
 Is this correct? I may have missed something really obvious in a 
quick

read of the paper…..

Thanks!

Bob


All the filtering and down mixing is done in the digital domain.
Anitialiasing filters in front of the ADCs are also be required.

A 2  (or more) receive channel SDR board would be a nice tool to use 
for this

provided the FPGA is large enough.

Bruce



> On May 25, 2016, at 12:01 PM, Sherman, Jeffrey A. (Fed)
>  wrote:
>
> Hello,
>
> A recently published paper might be of interest to the time-nuts
> community. We studied how well an unmodified commercial software defined
> radio (SDR) device/firmware could serve in comparing high-performance
> oscillators and atomic clocks. Though we chose to study the USRP
> platform, the discussion easily generalizes to many other SDRs.
>
> I understand that for one month, the journal allows for free electronic
> downloads of the manuscript at:
> http://scitation.aip.org/content/aip/journal/rsi/87/5/10.1063/1.4950898
> (Review of Scientific Instruments 87, 054711 (2016))
>
> Afterwards, a preprint will remain available at:
> http://arxiv.org/abs/1605.03505
>
> There are commercial instruments available with SDR architecture
> under-the-hood, but they often cost many thousands of dollars per
> measurement channel. In contrast, commercial general-purpose SDRs scale
> horizontally and can cost <= $1k per channel. Unlike the classic
> dual-mixer time-difference (DMTD) approach, SDRs are frequency agile. The
> carrier-acceptance range is limited not by the sample clock rate but by
> the ADC's input bandwidth (assuming one allows for aliasing), which can
> be many times greater. This property is an important feature in
> considering the future measurement of optical clocks, often accomplished
> through a heterodyne beatnote (often at "practically any" frequency
> between ~1 MHz to 500 MHz) with a femtosecond laser frequency comb. At
> typical microwave clock frequencies (5 MHz, 10 MHz), we show that a stock
> SDR outperforms a purpose-built DMTD instrument.
>
> Perhaps the biggest worry about the SDR approach is that fast ADCs are in
> general much noisier than the analog processing components in DMTD.
> However, quantization noise is at least amenable to averaging. As you all
> likely appreciate, what really limits high precision clock comparison is
> instrument stability. In this regard, the SDR's digital signal processing
> steps (frequency translation, sample rate decimation, and low-pass
> filtering) are at least perfectly stable and can be made sufficiently
> accurate.
>
> We found that in the studied units the limiting non-stationary noise
> source was likely the aperture jitter of the ADC (the instability of the
> delay between an idealized sample trigger and actuation of the
> sample/hold circuitry). However, the ADC's aperture jitter appears highly
> common-mode in chips with a second "simultaneously-sampled" input
> channel, allowing for an order-of-magnitue improvement after
> channel-to-channel subtraction. For example, at 5 MHz, the SDR showed a
> time deviation floor of ~20 fs after just 10 ms of averaging; the
> aperture jitter specification was 150 fs. We also describe tests with
> maser signals lasting several days.
>
> Best wishes,
> Jeff Sherman, Ph.D.
> 
> National Institute of Standards & Technology
> Time and Frequency Division (688)
> 325 Broadway / Boulder, CO 80305 / 303-497-3511
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Re: [time-nuts] Simple solution for disciplining OCXO with 1 PPS

[djl]

I like the little boards at:
http://navspark.mybigcommerce.com/development-boards/
It's a GPS with a fully programmable 32-bit Arduino-compatible 
processor. $22
Crowdsourced about 3 yr ago, matured now. Various versions; you can even 
have Beidou :-).

Don


On 2016-05-22 19:45, Tom Van Baak wrote:

Can a pure analog design access the sawtooth correction?  My GPS
receivers send sawtooth as a digital message on a serial port.   I
don't know if saw tooth correction is required to meet his spec.


Hi Chris,

Many GPS/1PPS receivers don't output sawtooth information and yet they
work really well. Sawtooth correction isn't necessary except for
high-end GPSDO. The same is true for zero-D timing mode.

Examples include:
https://www.adafruit.com/products/746
https://www.parallax.com/product/28509
as well as any number of equivalent GPS/1PPS boards at half the price
on eBay. See also:
http://www.leapsecond.com/pages/MG1613S/

In fact many simple GPSDO rely on sawtooth dither to improve their
performance; that is, it's a feature to be exploited, not a bug to be
corrected for.

A dirt cheap GPS receiver these days may have 1PPS error of 20 ns RMS.
Over 1000 s integration that's 2e-11 in frequency stability; far
better than the OP's modest target of 1e-10 at an hour.

Here's another thought. OP wants STS of stability of 1e-10 at an hour.
No mention of accuracy, or long-term performance. So if stability is
all that's needed I would just use a old 10811-class OCXO, perhaps one
that's been running faithfully for a few weeks or months. That will
get you 1e-10 at an hour without any GPS any antenna any analog any
digital any complexity any tuning.

/tvb

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Re: [time-nuts] Precise Time transfer and relative position over a short baseline

[djl]

I have not followed this closely. Why not use the data itself? The 
theoretical pattern for the telescope pair can be calculated. Even 
though the signals are not i.i.d, from phototubes, the data can be slid 
along and the delay pattern established and compared to the theoretical 
pattern?  Timing is then important for "pointing". Certainly the 
compared signals can be used in any case to correct timestamps.
Sorry if this has been mentioned before, in that case, great minds run 
in the same track :-) :-)

Don


On 2016-04-11 00:58, Ilia Platone wrote:

As alternative to independent clocks and single photon tagging, we
considered to use TDCs: a possible solution would be radio cross links
between the telescopes that drive the start/stop signals of the TDCs,
then we'd tag only the lapses between photon detection from each
telescope. In this way a single clock would be used on a receiving and
recording station.

Is this a good solution?
Regards,
Ilia.

Il 11/04/2016 07:00, Bruce Griffiths ha scritto:
There is a proposal to use multiple light bucket style optical 
telescopes to do Intensity stellar Interferometry over short baselines 
(up to perhaps 1km  or so) by using independent clocks to time tag 
photon  arrivals. store the time tags and process the data off line. 
Depending on the time tag resolution there is a need to measure the 
time differences between the independent clocks to an accuracy in the 
1ns to 100ps range. Is there a better way of doing this other than 
using geodetic grade GPS receivers capable of GPS carrier phase 
measurements?Since the local clock flywheel oscillators will need to 
not deviate by more than 100ps or so over the several minutes required 
to perform the carrier phase averaging what sort of clock will be 
suitable apart from a good rubidium standard with a cleanup 
oscillator?

NB Running fibres or coax between the telescopes isnt an option.

The relative positions of the telescopes has to be known to within a 
cm or so for this to work.

Bruce

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Cell +39 349 1075999
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Re: [time-nuts] FEI-5660 Rubidium Oscillator

[djl]

granite is not only radioactive, but also piezoelectric.

Dpn

On 03/29/2014 12:48 PM, Magnus Danielson wrote:

On 28/03/14 04:47, Mark Sims wrote:
no, No, NO granite!  Granite tends to be rather radioactive 
(particularly avoid the pink stuff).  Any audiofool worth his tin 
ears can't have no stinkin' alpha/beta/gamma particles mucking with 
his music!


In that case you don't want a Rubidium clock in there.
Rb-87 has a 48,8 miljard years half-time with beta- emission.

Then again, it's about three times the life of universe, so it's not a 
very strong radioactive source. :)


Cheers,
Magnus
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Re: [time-nuts] GPSDO simulation tool

[djl]

Well done!
Don

On 03/21/2014 03:55 PM, Tom Van Baak wrote:

Designing a GPSDO is a permanent topic of time-nuts, and always invites lots of 
opinions and methods.

The net performance of a microcontroller-based GPSDO is mostly due to the 
following ingredients:
- the stability of the OCXO (or TCXO or Rb or whatever the LO is)
- the stability of the GPS 1PPS (including sawtooth correction, or not)
- the disciplining algorithm itself, and user-settable configuration parameters 
or filtering
- the finite resolution of the TIC or phase comparator
- the finite resolution of the DAC/EFC

Normally what happens is that someone spends weeks or months or even years 
working on each of these ingredients, measuring, comparing, tweaking, or maybe 
just hoping for the best. These measurements can take a lot of time, or be 
difficult to replicate.

I have an alternative.

It's a simple software tool which takes *real* GPS phase data, and *real* LO 
phase data, and a *real* GPSDO algorithm(s) -- along with optional resolution 
of the TIC and optional resolution of the DAC -- and then creates GPSDO phase 
data through *simulation*. You can then plot this virtual GPSDO phase data with 
Stable32 or Plotter or TimeLab or your favorite phase / frequency / stability 
tool.

So instead of waiting hours and days to test your new filtering idea, or your 
new GPSDO algorithm, or to compare the effect of a 10 ns vs. 1 ns vs. 100 ps 
vs. 10 ps TIC, or to compare the effect a 10-bit vs. 16-bit vs. 24-bit DAC -- 
you just run the simulation on your PC and get an answer in a few seconds.

Have a look and let me know what you think. The tool is gpsim1.c (Windows: 
gpsim1.exe) under:
 http://www.leapsecond.com/tools/

For this to work, one needs actual GPS data and actual LO data. I have a 
growing collection of sample data files here:
 http://www.leapsecond.com/pages/gpsdo-sim/

For example, if you run this command:
 gpsim1  gps-mtk3339.txt  ocxo.dat  gpsdo.txt

and use TimeLab to plot these three files, you will get the attached plot. No 
solder, no instruments, no antenna, no waiting, no guessing. A complete 4-day 
simulation takes just 3 seconds (on my 10-year old laptop). Load the simulated 
phase data with 'L' in TimeLab and view phase, frequency, ADEV, MDEV, TDEV. 
Answer your GPSDO design questions in minutes instead of weeks.

Try different parameters. Try different GPS boards. Try different oscillators. 
See if you can make the best ADEV. Try new disciplining algorithms. Make the 
PID more complex. Change the filtering.

/tvb


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