Discussion:
XKCD on time
(too old to reply)
Martin VE3OAT
2018-09-28 17:53:57 UTC
Permalink
I love GMT. All of this UTC stuff is ... revisionist!
My cheque is in the mail.
... Martin VE3OAT
When I am global dictator, we will all run on GMT and all time
zones, summer time, DST and similar nonsense will be abolished.
I am accepting campaign donations! ?
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Artek Manuals
2018-09-28 18:54:30 UTC
Permalink
David

1) Before I make a donation what is your plan to control the millennial's ?

2) Could we outlaw solid state electronics (or at least custom IC's) and
go back to vacuum tubes while we are at

Dave
I love GMT.  All of this UTC stuff is ... revisionist!
My cheque is in the mail.
... Martin    VE3OAT
When I am global dictator, we will all run on GMT and all time
zones, summer time, DST and similar nonsense will be abolished.
I am accepting campaign donations!  ?
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Dave
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www.ArtekManuals.com


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David Van Horn
2018-09-28 19:11:05 UTC
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By expanding facebook significantly, I plan to keep the millennials occupied in such a way that they are peaceful, happy, and complacent.
Ad revenues could support the whole program.

Solid state electronics seems to be something we will need to tolerate, but we can require tubes to be allowed to participate.

😊

-----Original Message-----
From: time-nuts <time-nuts-***@lists.febo.com> On Behalf Of Artek Manuals
Sent: Friday, September 28, 2018 12:55 PM
To: time-***@lists.febo.com >> skipp via time-nuts <time-***@lists.febo.com>
Subject: Re: [time-nuts] XKCD on time

David

1) Before I make a donation what is your plan to control the millennial's ?

2) Could we outlaw solid state electronics (or at least custom IC's) and go back to vacuum tubes while we are at

Dave
I love GMT.  All of this UTC stuff is ... revisionist!
My cheque is in the mail.
... Martin    VE3OAT
When I am global dictator, we will all run on GMT and all time
zones, summer time, DST and similar nonsense will be abolished.
I am accepting campaign donations!  ?
_______________________________________________
to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
--
Dave
***@ArtekManuals.com
www.ArtekManuals.com


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Artek Manuals
2018-09-28 19:47:15 UTC
Permalink
Hmmmm .... Farce-Book.... hadn't considered that approach .. some sort
of (ready for this )

"subliminal millennial  mind control" !!

 The gnomes and I will go to work on it immediately !

-DC
Post by David Van Horn
By expanding facebook significantly, I plan to keep the millennials occupied in such a way that they are peaceful, happy, and complacent.
Ad revenues could support the whole program.
Solid state electronics seems to be something we will need to tolerate, but we can require tubes to be allowed to participate.
😊
-----Original Message-----
Sent: Friday, September 28, 2018 12:55 PM
Subject: Re: [time-nuts] XKCD on time
David
1) Before I make a donation what is your plan to control the millennial's ?
2) Could we outlaw solid state electronics (or at least custom IC's) and go back to vacuum tubes while we are at
Dave
I love GMT.  All of this UTC stuff is ... revisionist!
My cheque is in the mail.
... Martin    VE3OAT
When I am global dictator, we will all run on GMT and all time
zones, summer time, DST and similar nonsense will be abolished.
I am accepting campaign donations!  ?
_______________________________________________
to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
--
Dave
www.ArtekManuals.com
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Dave
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Dana Whitlow
2018-09-28 20:30:04 UTC
Permalink
David Van Horn,

You're on the right track, but what would you do about those pesky leap
seconds?

Dana
Post by Artek Manuals
Hmmmm .... Farce-Book.... hadn't considered that approach .. some sort
of (ready for this )
"subliminal millennial mind control" !!
The gnomes and I will go to work on it immediately !
-DC
Post by David Van Horn
By expanding facebook significantly, I plan to keep the millennials
occupied in such a way that they are peaceful, happy, and complacent.
Post by David Van Horn
Ad revenues could support the whole program.
Solid state electronics seems to be something we will need to tolerate,
but we can require tubes to be allowed to participate.
Post by David Van Horn
😊
-----Original Message-----
Manuals
Post by David Van Horn
Sent: Friday, September 28, 2018 12:55 PM
Subject: Re: [time-nuts] XKCD on time
David
1) Before I make a donation what is your plan to control the
millennial's ?
Post by David Van Horn
2) Could we outlaw solid state electronics (or at least custom IC's) and
go back to vacuum tubes while we are at
Post by David Van Horn
Dave
Post by Martin VE3OAT
I love GMT. All of this UTC stuff is ... revisionist!
My cheque is in the mail.
... Martin VE3OAT
When I am global dictator, we will all run on GMT and all time
zones, summer time, DST and similar nonsense will be abolished.
I am accepting campaign donations! ?
_______________________________________________
to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
--
Dave
www.ArtekManuals.com
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Dave B via time-nuts
2018-10-01 08:03:05 UTC
Permalink
Many thanks to all the respondents to my question.

Nice to know I can still think some things through in a good way!  ;-)

Re the below..

Yes, I should have said "dual trace" not "dual beam".  "My bad" as some say.

I should know better, having spent some 3 1/2 years of my life as
in-house service serf at Tek here in the UK (Harpenden and Maidenhead)
towards the end of the transition between the venerable "steam driven"
500 series (Valved, or Tubed 'scopes) and the then new-fangled solid
state equipment, I do indeed know how the 465 (and a lot of other Tek
products of that era) work, and it's differences to the true "dual beam"
instruments (such as the 556 and so on.)

Also, as an RF guy, coax run's are always terminated where so needed at
times like this, and trigger points set-up to be as close to the mid
point of the sharpest edge of a clock signal as possible.  (Taking note
of the specification of whatever is producing it, so as not to get hit
by any pulse width jitter that may be a "known feature" etc.)  In this
instance, two sinusiods, so I chose the rising edge, just because ...

Though it is not "needed" to show two signals on screen at the time, it
is a lot easier (on the eye) to compare one signal drifting past another
(known frequency) signal, not relying on the otherwise excellent
graticule for the purpose I need.

In this instance, I'm more interested in the relative frequency between
the two sources, so the mk1 eyeball and trigger set-up is good enough
for my needs.

When the project is eventually deployed, it will be referenced to the
Thunderbolt and generate a sufficiently stable and accurate 20.45 (and
divisions of) MHz clock for other equipment.

But interesting reading none the lest.

Thanks very much again to all respondents.

Much appreciated.

Dave B. (G0WBX)

PS:    I do like the idea of setting up a camera to take a photo of the
'scope every hour or so!  Not practical for many I guess, but it
illustrates the point well.   But the aliasing opportunity I think would
be perhaps too great, in essence being a sampled data system by then.  
Also, one then needs an accurate 1 hour timer!   And so it goes on ;-)


------------------------------------------------------------------------
Subject: Re: [time-nuts] A silly question ...
Content-Type: text/plain; charset="utf-8"
Triggering a dual beam 'scope (Tek 465) from the TB on Ch1, and having> the output of the OCXO on Ch2, the resulting display on Ch2 of course> drifts in relation to the static waveform on Ch1. (Both nice
sinusoids.)
The Tek 465 analog cathode ray oscilloscope was/is a very flexible
instrument. But this flexibility allows you to set up the instrument in
ways which will not allow this commonly used oscillator comparison
technique to work correctly. Since you are interested in these
instruments, here are some details about setting up the instrument for
such comparisons.
(1) The Tek 465 is not a dual beam oscilloscope. Dual beam oscilloscopes
(such as the Tektronix 556 and 7844) use a special CRT which
incorporates two independent electron guns. Each electron gun
--
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a
Tom Van Baak
2018-10-01 08:38:01 UTC
Permalink
Post by Dave B via time-nuts
Dave B. (G0WBX)
PS: I do like the idea of setting up a camera to take a photo of the
'scope every hour or so! Not practical for many I guess, but it
illustrates the point well. But the aliasing opportunity I think would
be perhaps too great, in essence being a sampled data system by then.
Also, one then needs an accurate 1 hour timer! And so it goes on ;-)
For hourly photos consider using a webcam or smart phone & time-lapse photo app.

Here's an example of measuring time drift in mains with a photo every 15 minutes. Watch how the red seconds hand drifts by up to 4 seconds during the day: Loading Image...

About the aliasing, yes, one must keep that in mind. If the drift between your 10 MHz signals is erratic or if you slip by more than half of 100 ns per hour there could be ambiguity in your interpretation of the photos. That aliasing must be avoided.

There are two easy solutions:
1) Take a photo more often than once per hour. For example, once a minute improves the possibility of ambiguity by a factor of 60.
2) Divide the frequency from 10 MHz to 100 kHz. Now your cycles are 10 us instead of 100 ns, which reduces the chance of undetected cycle slip by a factor of 100.

Taking this to an extreme, imagine taking a photo every second, and imagine dividing your 10 MHz down to 1 Hz. Now you've reduced the chances of aliasing by tens of billions. And ... now you know why almost all timing measurements are done with a TIC as the "camera" and 1PPS as the "cycle".

This is also why, since 1972, UTC does time jumps (aka leap seconds) in steps of exactly 1 second instead of any smaller value -- it perfectly fools all the TIC's in the world.

/tvb


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Peter Vince
2018-10-01 09:14:55 UTC
Permalink
Tom - I love the idea of taking (a series of) accurately timed
photograph(s), but have no idea how to go about it - can you please explain
how you did it for your mains-driven clock?

Peter (London)


On Mon, 1 Oct 2018 at 09:39, Tom Van Baak <***@leapsecond.com> wrote:
...
Post by Tom Van Baak
For hourly photos consider using a webcam or smart phone & time-lapse photo app.
Here's an example of measuring time drift in mains with a photo every 15
minutes. Watch how the red seconds hand drifts by up to 4 seconds during
the day: http://leapsecond.com/pages/tec/mains-clock-ani.gif
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Tom Van Baak
2018-10-01 10:09:38 UTC
Permalink
Tom - I love the idea of taking (a series of) accurately timed photograph(s), but have no idea
how to go about it - can you please explain how you did it for your mains-driven clock?
Hi Peter,

During that year I collected lots of mains timing data. There are many ways to do that; in my case I measured the precise time of every 60th zero-crossing against my house standard [0]. From that you can make any number of graphs of accumulated mains time error over a day, or month, or year. Or make histogram plots of mains frequency distribution. Or ADEV plots, etc. And while those plots are all technically accurate, they don't emotionally convey the live jitter and wander that ones sees in a mains sinewave. So that's when I came up with the goal to make a short time-lapse movie showing how changes in mains frequency affect a typical wall clock.

The method was rather crude. I used a tripod and webcam so that each frame showed both the mains-drive 12h analog clock in the center and a cesium-driven 24h digital clock in the lower left. The window shade in the background indicated if it was day or night (IIRC that was accidental but it was a nice touch). To capture an image exactly every 15 minutes, I wrote a PC script that included a precise timer and URL fetch. It was probably good to 0.1 second of UTC. I then used an ancient MS program called GIFAnimator.exe to assemble the individual images into the 1/4 second per frame movie.

You could do the same today using a mix of RPi, NTP, cron, wget/curl, etc. Or there's probably some cool Python library that does webcam time lapse movies in one line of code. In my case I used an old Windows XP laptop; the precise timer was alarm.exe [1], the web fetch tool was url.exe [2], and instead of NTP the PC jam syncs [3] to NIST every 5 minutes. I wouldn't recommend using these fragile play tools, but they're out there in my tools directory if you want to have a look.

/tvb

[0] By "house standard" I mean whatever your best 10 MHz / 1PPS source is at home; Rb, Cs, GPSDO, etc.
[1] http://leapsecond.com/tools/alarm.c (alarm.exe)
[2] http://leapsecond.com/tools/url.c (url.exe)
[3] http://leapsecond.com/tools/daytime.c (daytime.exe)



----- Original Message -----
From: Peter Vince
To: Tom Van Baak ; time-***@lists.febo.com
Sent: Monday, October 01, 2018 2:14 AM
Subject: Timed photography (was: Re: [time-nuts] A silly question ...)


Tom - I love the idea of taking (a series of) accurately timed photograph(s), but have no idea how to go about it - can you please explain how you did it for your mains-driven clock?


Peter (London)


On Mon, 1 Oct 2018 at 09:39, Tom Van Baak <***@leapsecond.com> wrote:
...
For hourly photos consider using a webcam or smart phone & time-lapse photo app.
Here's an example of measuring time drift in mains with a photo every 15 minutes. Watch how the red seconds hand drifts by up to 4 seconds during the day: http://leapsecond.com/pages/tec/mains-clock-ani.gif
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Achim Gratz
2018-10-01 19:18:00 UTC
Permalink
Post by Peter Vince
Tom - I love the idea of taking (a series of) accurately timed
photograph(s), but have no idea how to go about it - can you please explain
how you did it for your mains-driven clock?
For video you'd need to start with a camera that has a genlock interface
and then frame-sync it on top of the syntonization provided by the
genlock. I'm not sure the current consumer crop would provide an
interface to do that. For still pictures, external triggers are
available even on some low-end cameras, although you might need to
experiment a bit to figure out exactly what the delay is and whether it
is changing with the exposure settings. That should be good to time the
trigger to a few dozen ms and a bit better if the exposure conditions
can be fixed, higher precision usually requires specialized cameras. A
tried solution in high-speed photography is to use an open shutter (or
one way slower than you need) and just (strobo-)trigger the flash, which
can usually be more precisely controlled (plus it's easier to figure out
when it actually triggered so you can remove systematic offsets). If
you're serious about it, external high-speed shutters that can be
triggered more precisely than most cameras also exist.


Regards,
Achim.
--
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

DIY Stuff:
http://Synth.Stromeko.net/DIY.html

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