[time-nuts] How good is the left end of your ADEV curve?

[Hal Murray]

way way way left.

Ray Weiss was the speaker at the Stanford Physics Colloquium today.  In case 
you don't recognize the name, he is one of the leaders of the LIGO project 
that detected gravity waves about a year ago.

He's a good speaker with a neat topic.  He spent a lot of time giving credit 
to other people.

One of the far-out future ideas he mentioned was collecting data on lots of 
pulsars.  If you could get good enough data, maybe you could see gravity 
waves wandering around the universe.  (Maybe leftover from the big bang.  I 
didn't catch that part.)

The time scale is months or years.  Micro Hertz.  The unit for wavelength 
would be light-years.

How long will it be before we need a gravity-nuts list?

-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Autodesk Eagle -- maybe they're listening

[Bob Camp]

Hi

The big gotcha in moving between these programs is porting the libraries. 
Without moving them over, you have very limited options when working in 
the “new” environment. 



Opened up the email this evening and *surprise* a discount coupon from 
Autodesk. Charge a lot as a “standard” price and then discount it 50%. 
Somehow this reminds me a lot of the local furniture sales  .. errr.. SALES …
errr..  Yes, it’s a brave new world.

Bob


> On Jan 24, 2017, at 2:12 PM, Hal Murray  wrote:
> 
> 
> ke9h.gra...@gmail.com said:
>> So a learning curve to get up on KiCad and, for me, an issue migrating ten
>> years personal library of component foot-prints. 
> 
> The Eagle files are store in simple text.  If there isn't already an Eagle to 
> KiCad translator, I'd expect one soon.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Autodesk Eagle -- maybe they're listening

[Hal Murray]

ke9h.gra...@gmail.com said:
> So a learning curve to get up on KiCad and, for me, an issue migrating ten
> years personal library of component foot-prints. 

The Eagle files are store in simple text.  If there isn't already an Eagle to 
KiCad translator, I'd expect one soon.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Autodesk Eagle -- maybe they're listening

[Graham / KE9H]

Or, switch to the best "free" open source solution, which is KiCad.

Eagle had a bunch of quirks.  I hear KiCad has a different set of quirks.

So a learning curve to get up on KiCad and, for me, an issue migrating ten
years personal library of component foot-prints.

I heard a blogger suggest that if you move to KiCad, make a donation in the
amount of the old $69 Eagle license fee to the KiCad development team.

--- Graham

==



On Mon, Jan 23, 2017 at 10:01 PM, jimlux  wrote:

> On 1/23/17 4:56 PM, Mike Suhar wrote:
>
> Looks like they have a student version but the way I read it you have to
>> actually be a student enrolled in an education institution.  I assume they
>> require some form of proof.
>>
>>
> The usual hack for that is to enroll in a single class at the local
> community college, which you don't need to pass, just enroll, so you get
> the student ID.
>
>
>
>
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Re: [time-nuts] Allan Variance with an HP53132a counter

[Tom Van Baak]

> I developed a home-brewed OCXO crystal oscillator disciplined with a long 
> wave radio
> station signal (162 kHz). Its working quite well with a long term stability 
> that is
> « probably » better than 10E-8 which I am actually looking forward to better 
> understand.
> I am considering using an HP53132 counter for this purpose, although I 
> understand that>
> it may not be the most recommended approach….

Hi Gilles,

1)
The HP53132 is fine for this application. 1e-8? No problem at all.

For distortion-free, long-term, automated measurements use the counter in TI 
mode instead of FREQ or PER mode. This is very simple: just divide your 162 kHz 
signal down to, say, 1 Hz and then compare that against a reference 1 Hz, such 
as a GPS 1PPS. That way you get a clean [phase difference] time series of your 
clock against GPS.

Your raw data is directly importable into TimeLab [1] and from that you will 
get correct phase / frequency / stability plots. The jitter in the GPS/1PPS 
will "drop out" quickly, especially if your OCXO is only 1e-8.

2)
In this case you only need a plain GPS board with 1PPS [2] [3]. Lots of these 
on eBay in the $20 to $40 range as well [4]. In other words, you do not need a 
GPSDO; at this stage of your being a time nut that only adds new layers of 
complication. So just compare phase and keep it simple.

3)
If you want lower cost, or more resolution than a HP53132, consider John's new 
TICC board [5], which will match and even out-perform the 53132. Both the 53132 
and TICC are directly usable into TimeLab.

/tvb

[1] http://www.ke5fx.com/timelab/readme.htm
[2] https://www.adafruit.com/product/746
[3] https://www.parallax.com/product/28509
[4] for example, search eBay for LEA-6T and search the web for LEA-6T threads
[5] https://www.tapr.org/kits_ticc.html


- Original Message - 
From: "Gilles Clement" 
To: 
Cc: "Gilles Clement FREE" 
Sent: Sunday, January 22, 2017 6:52 AM
Subject: [time-nuts] Allan Variance with an HP53132a counter


Hi, 

I am new to this list and have been following it for a while with great 
interest. I am afraid I am getting contaminated with the "TN" virus… !

I developed a home-brewed OCXO crystal oscillator disciplined with a long wave 
radio station signal (162 kHz). Its working quite well with a long term 
stability that is « probably » better than 10E-8 which I am actually looking 
forward to better understand. I am considering using an HP53132 counter for 
this purpose, although I understand that it may not be the most recommended 
approach….

Please find hereafter the rationale: 
- The HP53132 implements a triangular averaging algorithm (Delta averaging) in 
its standard frequency or period measurement mode of operation 
- This feature provides a pretty high resolution (up to 0.5*10E-12 if I am 
correct) which should be appropriate at least to get a first idea of the 
oscillator performance
- But it comes with the drawback that an Allan Variance computed directly from 
such frequency (or period) readings, would be distorted with respect to the 
"standard" Allan Variance (which assumes a PI averaging instead of a Delta 
averaging algorithm to compute the fractional frequencies)
- However, from the Australian paper titled : « Considerations on the 
Measurement of the Stability of Oscillators with Frequency Counters » I noticed 
that:
When I look at OCXO crystals oscillator stability discussions in the 
literature, White Frequency, Flicker Frequency and Random Walk Frequency seem 
to be the dominant noise factors considered (ex: in phase noise spectral 
density graphics)
The distortion from Allan Variance to Delta Variance is limited for White 
Frequency, Flicker Frequency and Random Walk Frequency noises (though it can be 
several orders of magnitudes for White Phase and Flicker Phase noises)
Moreover formulas are provided in the paper to evaluate the amount of such 
distortions. The impact appears to be a simple multiplier of 1.33, 1.30 and 
1.15 for the three corresponding noises, the slopes of the curves are not 
impacted (i.e: tauE-1 ; tauE+0 and tauE+1)
- So the idea is the following: start with a simple bench test, reading the 
standard mode of Periods measurement, calculate the "naive" Triangular Variance 
from these data, identifying the noise types (according to the slope of the 
curve sections), and applying the corresponding offset correction, hopefully 
leading to an estimate of the "standard" Allan Variance.  
- This approach would have the great advantage to be simple and cost effective, 
as one can find nowadays second hand 53132’s at reasonable cost even with the 
(mandatory) OCXO option.  

Comments welcomed, 
Best, 
Gilles. 

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Re: [time-nuts] purpose of time of day display units

[John Clark]

Hello Ruslan,

Thanks for posting the picture and prompting the discussion.

We're the OEM of the amber and blue 1RU displays shown at the top of the racks 
and I can confirm that those are time-code driven displays.

The displays can be used as a confirmation of valid code for distribution - we 
can set the displays to show dashes upon a loss of valid reference and this 
gives an easy, quick indication to an operator that their TC isn't being 
distributed properly.

They've also got the displays set up to show local time/date while the red 1RU 
display to the left is showing UTC.  Many installations will have multiple 
flavors of time code being distributed and they may want an easy reference as 
to which is UTC vs. others and the displays are a good visual confirmation for 
them.

Additionally, all of our displays can also be used as countdown/up systems as 
well whether through software integration or using our count controllers and 
many operators utilize the count function within their applications in addition 
to the time and date.

My best,

John Clark
Masterclock, Inc.

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Ruslan 
Nabioullin
Sent: Sunday, January 22, 2017 12:31 AM
To: time-nuts@febo.com
Subject: [time-nuts] purpose of time of day display units

Hi, looking at pictures of various time metrology equipment setups for best 
practices and inspiration, I have commonly seen time of day display
unit(s) installed in racks containing processing or time transfer equipment, 
e.g., http://www.xyht.com/wp-content/uploads/2015/05/Powers_Master_Clock.jpg. 
All that these units do is merely display the time of day and sometimes the 
date, typically by means of seven segment LED displays, of the time code 
inputted to them (typically IRIG-B, I'm guessing).  Any ideas why such a unit 
is necessary when one can simply look at the time displayed by timing receivers 
and time code generators (and even some standards), and the interface of some 
fusor, defined in this context as a system which performs timing data fusion 
(by implementing a paper clock or a more primitive algorithm) and timekeeping, 
either by means of a direct shell, or via something like NTP?

Thanks in advance,
Ruslan
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Re: [time-nuts] Thermal effects on cables

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 23 January 2017 at 17:29, Tim Shoppa  wrote:

>
> Funny how people always want to put the words "dielectric" and "constant"
> right next to each other but we know it isn't constant :-)
>
> Tim N3QE
>

Yes. I will have to look into this, as I see some quite widely different
values quoted for the dielectric constant of PTFE. I have an HP 4291B
impedance/material analyzer

http://www.keysight.com/en/pd-100857%3Aepsg%3Apro-pn-4291B/rf-impedance-material-analyzer?cc=US=eng=true=4291b

and  16453A dielectric material test fixture

http://www.keysight.com/en/pd-100508%3Aepsg%3Apro-pn-16453A/dielectric-material-test-fixture?cc=US=eng

To make a measurement of the permittivity of a material, the calibration
procedure is a bit complicated, needing 6 or 7 standards, but at one point
you need to use a dielectric of known thickness and known permittivity. I
believe it defaults to 2.1, which is supposed to be what the bit of PTFE
Keysight supply is. Needless to say I don't have that, and I'm not spending
the best part of £500 for a bit of PTFE that's 1 mm thick. But I've seen
values of Er of PTFE quoted from 2.0 to 2.2.

Dave
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Re: [time-nuts] Autodesk Eagle -- maybe they're listening

[Bob Camp]

Hi


> On Jan 23, 2017, at 8:28 PM, Jim Pruitt  wrote:
> 
> Mike,  you are correct about Autodesk products being free to
> students/faculty/and staff with proof of status.  A college/university
> email would do that.
> 
> I retired from a medium size state university here in late spring.  My job
> there was to purchase, set up, install/administer software and hardware,
> and maintain some application servers including ones for Autodesk,
> Solidworks, Matlab, and Oracle Primavera.  I had 2 Autocad labs consisting
> of about 25 stations each.  We used Autodesk products because they were
> free to universities as long as it was in a teaching capacity.  For that
> reason facilities management could not use the educational version.
> Autodesk and the cad labs took up over 75% of my time so 2 labs kept me
> busy and I had 10 other pc labs to maintain on campus.  I assume that
> because the product was free to us we were on the bottom of the food chain
> as I ran into a bug with their product that cause our students to have to
> sit for 20 minutes before the license server would issue them a license.

Even if you pay >$100K in license fees a year, don’t count on fast solutions
for things like license server nonsense (or any other bug). We are not in any
way an Autodesk customer at work so that’s not a direct knock on them. It’s
more a knock on the industry as a whole. With the payments we *do* get
a solution of some sort eventually. Two weeks is a more likely time period 
than “later today” for most of them. That *is* better than the “maybe never”
time frame for unpaid support. It still is not what you need …..

Bob



> Keep in mind that classes only lasted 50 minutes!  Even though I hired a
> third party VAR (value added reseller) for cad tech support.  Education was
> all on their own so even my VAR could not help me resolve the problem.
> They did manage to give me one name at Autodesk that I could contact and
> push them from inside.  If it had not been for that I feel they never would
> have taken the problem seriously.  Even at that it took 2 months to get it
> figured out.  They did not fix the problem til the following year when a
> new version was released.  Prior to the product being offered free I could
> contact Autodesk and get support when needed.
> 
> In short,  Autodesk products are free to students and staff/faculty when
> used for educational purposes.  I had to resort to forums and other avenues
> to get tech support.
> 
> Good luck.
> 
> Jim Pruitt
> 
> 
> On Mon, Jan 23, 2017 at 4:56 PM, Mike Suhar  wrote:
> 
>> Many companies are trying to jump on the subscription band wagon.  It is a
>> way to keep a steady flow of income.  Unfortunately,  hobbyists are left
>> out in the cold.   I have version 7.5 with the hobbyist license.  I just
>> tried to get 7.7 but the download pulls in version 8.0.  I did not install
>> it.
>> 
>> If you are not using the software on a regular basis I assume  you could
>> go  with the monthly subscription for a month then drop it.  Pick up again
>> a few months later when you start another project and need more than the
>> freeware capabilities.
>> 
>> Looks like they have a student version but the way I read it you have to
>> actually be a student enrolled in an education institution.  I assume they
>> require some form of proof.
>> 
>> Mike
>> W8RKO
>> 
>> -Original Message-
>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John
>> Ackermann N8UR
>> Sent: Monday, January 23, 2017 17:14
>> To: Discussion of precise time and frequency measurement
>> Subject: [time-nuts] Autodesk Eagle -- maybe they're listening
>> 
>> Autodesk just sent a follow-up to my "new price model unacceptable"
>> complaint a few days ago.  It looks like they are going to upgrade the
>> "Standard" subscription ($100/year) to support 4 layer boards up to 160
>> cm2, which I think matches the current standard version capabilities.
>> Here's a thread from the Autodesk forum:
>> 
>> http://forums.autodesk.com/t5/eagle-forum/a-path-forward-
>> for-the-make-license-a-step-up-for-standard/td-p/6823182
>> 
>> This is effective with the next release, which is supposed to be out in a
>> couple of weeks.  (In the meantime, I've made sure to download every flavor
>> of installer for version 7.7.0, just in case...)
>> 
>> 
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Re: [time-nuts] Thermal effects on cables

[Dr. David Kirkby (Kirkby Microwave Ltd)]

  oI On 23 Jan 2017 17:02, "REEVES Paul" 
wrote:
>
> Hi David,

Hi Paul

> Surely the impedance of the cable is only affected by the ratio of the
inner conductor and outer conductor diameters modified by the internal
dielectric constant, nothing to do with the frequency of operation.

No, that is incorrect.

There are two complications with coax, which mean that you can't trust the
"normal" equations at very low or very high frequencies.

1) LOW FREQUENCY

An accurate equation for the impedance of the cable is

Zo=sqrt ((R+j w L)/(G+j w C))

w = 2 Pi f
R = Resistance per metre (ohms/metre)
C = Capacitance per metre (Farads/metre)
G = Conductance per metre (Mho/metre)

If the frequency is high enough (above a few MHz),

j w L >> R and
j w C >>  G

so the R & G terms are insignificant and one gets the usual equation we know

Zo=sqrt (L/C)

At low frequencies the assumption that the resistive losses (R) are
insignificant is no longer valid, so impedance rises at frequency
decreases.

At DC a bit of coax is just a capacitor..

2) HIGH FREQUENCY

At high frequencies!the best of9 higher order modes can propagate.  The
reasons for this are more complicated to explain,  but are a result of the
breakdown of the assumption of the boundary conditions used to arrive at
the impedance.

The maths of this effort is more complicated,  needing Bessel functions.

> You might well have problems converting the larger diameters down to a
suitable size for the connectors at the higher frequencies though

Yes, but small connectors are used for the very same reason small cables
must be used.

> I thought that the HP cabling for the 8510 series VNAs was air spaced but
I might well be wrong - I just tried not to damage them :-)

You might well be right about the air spacing.  Of course there needs to be
some support for the centre conductor,  but it might be  beads like in 3.5
mm connectors. I really don't know.

> Regards,
>
> Paul Reeves

Dave, G8WRB.
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Re: [time-nuts] LEA-6T effect of position hold

[Attila Kinali]

On Tue, 24 Jan 2017 07:48:10 +0100
Ole Petter Ronningen  wrote:


> Thinking about a GPSDO, it is easy to see the difference between using the
> first half of the plot to discipline an oscillator versus the second half.
> 
> In case the attachment does not make it though, it is also here:
> http://www.efos3.com/images/AHM%20v%20PPS%20pos%20hold.PNG

Said Jackson reported a similar outcome a couple of years ago:

https://www.febo.com/pipermail/time-nuts/2012-December/073373.html
https://www.febo.com/pipermail/time-nuts/2012-December/073416.html
https://www.febo.com/pipermail/time-nuts/2013-March/074979.html


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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