On 2023-11-06 00:48, whit3rd wrote:
> On Sunday, November 5, 2023 at 11:51:23&#8239;AM UTC-8, Phil Hobbs wrote:
>> On 2023-11-01 21:48, whit3rd wrote:
>>> On Tuesday, October 31, 2023 at 4:14:41&#8239;PM UTC-7, John Miles, KE5FX wrote:
>>>> On Monday, October 30, 2023 at 9:01:17&#8239;PM UTC-7, Jan Panteltje wrote:
>>>>> How did you measure that 1 ps, seems just sales crap to me?
>>>>> Video digitizers have jitter depending on clock frequency..
>>>>> I have worked with those.
>>>> Digitize the delayed and original undelayed signals with a common clock,
>>>> then downconvert them to baseband I/Q with a complex DDS, then
>>>> band-limit the heck out of them. Then atan2() and unwrap them, and finally
>>>> subtract them to get the phase difference.
>>>>
>>>> The band-limiting step is the important one, as it gets rid of noise that would
>>>> otherwise show up as phase uncertainty. Once you get the measurement BW
>>>> down to a few Hz, picoseconds are trivial to resolve.
>>>
>>> Band-limiting is guaranteed if you FFT and look at a peak (initial process in most
>>> FFT work involves a Hamming window, which spreads a narrow frequency
>>> input into a few more channels) with correct statistical weighting.
>>> The "average" phase shift is the weighted average, and low-amplitude
>>> channels have high phase noise estimates, so the reciprocal of the
>>> square of the noise becomes a weight function for the averaging,
>>> and basically ignores off-peak values.
>>>
>> Once you've done the sampling, it's band-limited, all right, because all
>> the aliasing has happened already. Whether the transform resembles that
>> of the function you sampled depends on the function and how you filtered
>> it before sampling.
>>
>> Applying a window to the samples before taking the DFT just changes the
>> shape of the passband corresponding to each sample, _within_ the
>> fundamental interval.
> 
>   
> I'd say it does more than that; the time-series data fed into an FFT will
> pick up things like slow offset drifts in the input, which causes a step
> when the sample #1 is adjacent to sample #1024 (due to the discrete
> Fourier transform having a circular boundary condition).
> A sampling-time boundary step will contribute to lots of frequencies (all of them, in fact, because
> a step is the integral of a delta function).   Those artifacts ought not
> to contribute to a phase measurement, and lopping off half the samples'
> amplitudes with a Hamming window is the usual way to reject them.
> 

Windowing changes the shape of the passband of each frequency sample, we 
agree.  Doing it right means (in part) that the wraparound error is small.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Sunday, November 5, 2023 at 11:51:23&#8239;AM UTC-8, Phil Hobbs wrote:
> On 2023-11-01 21:48, whit3rd wrote: 
> > On Tuesday, October 31, 2023 at 4:14:41&#8239;PM UTC-7, John Miles, KE5FX wrote: 
> >> On Monday, October 30, 2023 at 9:01:17&#8239;PM UTC-7, Jan Panteltje wrote: 
> >>> How did you measure that 1 ps, seems just sales crap to me? 
> >>> Video digitizers have jitter depending on clock frequency.. 
> >>> I have worked with those. 
> >> Digitize the delayed and original undelayed signals with a common clock, 
> >> then downconvert them to baseband I/Q with a complex DDS, then 
> >> band-limit the heck out of them. Then atan2() and unwrap them, and finally 
> >> subtract them to get the phase difference. 
> >> 
> >> The band-limiting step is the important one, as it gets rid of noise that would 
> >> otherwise show up as phase uncertainty. Once you get the measurement BW 
> >> down to a few Hz, picoseconds are trivial to resolve. 
> > 
> > Band-limiting is guaranteed if you FFT and look at a peak (initial process in most 
> > FFT work involves a Hamming window, which spreads a narrow frequency 
> > input into a few more channels) with correct statistical weighting. 
> > The "average" phase shift is the weighted average, and low-amplitude 
> > channels have high phase noise estimates, so the reciprocal of the 
> > square of the noise becomes a weight function for the averaging, 
> > and basically ignores off-peak values. 
> >
> Once you've done the sampling, it's band-limited, all right, because all 
> the aliasing has happened already. Whether the transform resembles that 
> of the function you sampled depends on the function and how you filtered 
> it before sampling. 
> 
> Applying a window to the samples before taking the DFT just changes the 
> shape of the passband corresponding to each sample, _within_ the 
> fundamental interval.

 
I'd say it does more than that; the time-series data fed into an FFT will
pick up things like slow offset drifts in the input, which causes a step
when the sample #1 is adjacent to sample #1024 (due to the discrete
Fourier transform having a circular boundary condition).
A sampling-time boundary step will contribute to lots of frequencies (all of them, in fact, because
a step is the integral of a delta function).   Those artifacts ought not
to contribute to a phase measurement, and lopping off half the samples' 
amplitudes with a Hamming window is the usual way to reject them.

On 2023-11-01 21:48, whit3rd wrote:
> On Tuesday, October 31, 2023 at 4:14:41&#8239;PM UTC-7, John Miles, KE5FX wrote:
>> On Monday, October 30, 2023 at 9:01:17&#8239;PM UTC-7, Jan Panteltje wrote:
>>> How did you measure that 1 ps, seems just sales crap to me?
>>> Video digitizers have jitter depending on clock frequency..
>>> I have worked with those.
>> Digitize the delayed and original undelayed signals with a common clock,
>> then downconvert them to baseband I/Q with a complex DDS, then
>> band-limit the heck out of them. Then atan2() and unwrap them, and finally
>> subtract them to get the phase difference.
>>
>> The band-limiting step is the important one, as it gets rid of noise that would
>> otherwise show up as phase uncertainty. Once you get the measurement BW
>> down to a few Hz, picoseconds are trivial to resolve.
> 
> Band-limiting is guaranteed if you FFT and look at a peak (initial process in most
> FFT work involves a Hamming window, which spreads a narrow frequency
> input into a few more channels) with correct statistical weighting.
> The "average" phase shift is the weighted average, and low-amplitude
> channels have high phase noise estimates, so the reciprocal of the
> square of the noise  becomes a weight function for the averaging,
> and basically ignores off-peak values.
> 

Once you've done the sampling, it's band-limited, all right, because all 
the aliasing has happened already.  Whether the transform resembles that 
of the function you sampled depends on the function and how you filtered 
it before sampling.

Applying a window to the samples before taking the DFT just changes the 
shape of the passband corresponding to each sample, _within_ the 
fundamental interval.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Sat, 04 Nov 2023 06:03:22 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

>On a sunny day (Fri, 03 Nov 2023 07:32:12 -0700) it happened John Larkin
><jl@997PotHill.com> wrote in <1l0akipp3mla2hoqh3i04vd9njp41onrat@4ax.com>:
>
>>On Fri, 03 Nov 2023 05:22:04 GMT, Jan Panteltje <alien@comet.invalid>
>>wrote:
>>
>>>On a sunny day (Thu, 02 Nov 2023 07:39:42 -0700) it happened John Larkin
>>><jl@997PotHill.com> wrote in <snc7ki56n28ua94ck0hg20906kg0oejvi4@4ax.com>:
>>>
>>>>On Thu, 02 Nov 2023 04:16:52 GMT, Jan Panteltje <alien@comet.invalid>
>>>>wrote:
>>>>
>>>>>On a sunny day (Wed, 01 Nov 2023 07:56:13 -0700) it happened John Larkin
>>>>><jl@997PotHill.com> wrote in <0cp4ki1ui592aul2674qhmk85de16s8c3a@4ax.com>:
>>>>>
>>>>>
>>>>>>Here's a paper about the NIF timing system.
>>>>>>
>>>>>>https://www.slac.stanford.edu/econf/C011127/TUAP069.pdf
>>>>>>
>>>>>>The biggest error is the prop delay tempco of the fiberoptics, around
>>>>>>15 PPM/degC. The facility is BIG.
>>>>>>
>>>>>>https://en.wikipedia.org/wiki/National_Ignition_Facility
>>>>>>
>>>>>>I don't expect that laser fusion will ever be a practical power
>>>>>>source. NIF is actually mainly for weapons research.
>>>>>
>>>>>Thank you for the links.
>>>>>
>>>>>Billions of dollars it did cost I read...
>>>>>And the management knew it was crap...
>>>>
>>>>It's expensive but it works for the untended uses. It cost a fraction
>>>>of ISS and some other things I could name.
>>>>
>>>>>Example of the US Military Industrial Complex.
>>>>
>>>>One use is to keep a number of researchers busy understanding the
>>>>dynamics of nuclear weapons, refining simulations, now that we can't
>>>>test them any more.
>>>>
>>>>One thing I have noticed is that the big-science and space programs
>>>>seem to deliberately seek out small businesses as suppliers, and take
>>>>a chance on them.
>>>
>>>Sure, some new ideas can come in handy.
>>>
>>>
>>>>>
>>>>>As to fusion power, I am not even sure ITER will work this time...
>>>>>Probably needs to be rebuild a little bigger :-)
>>>>>
>>>>>Politics, job creation...
>>>>
>>>>Inefficient, but has at least some upside. I could name more expensive
>>>>programs that are flat destructive.
>>>
>>>Fighting climate change :-) ?
>>>
>>>
>>>As to timing, and I remember we discussed this before many years ago,
>>>in the sixties in the TV studio where I had to keep things running, it was all about timing.
>>>Mostly tubes in that old studio, some transistors.
>>>When a video link from a remote location was used
>>>it needed to be precisely in sync with the studio so they could cross-fade.
>>>So you have a complex in time signal, vertical interval, horizontal sync, color burst and for color 4.43 MHz here.
>>>To get things in sync we send carrier via one of the FM radio stations back to the remote location
>>>that steered their clock generator until both frame and horizontal sync were aligned at out place.
>>>Then we could cross-fade.
>>>As you likely need sync at only one point, where the laser beams hit, one could use a low power laser and a detector
>>>and use a complex signal that could be compared to adjust any remote electronics so the pulses at the 'blast'
>>>place would be guaranteed to be in sync.
>>>Fifties, sixties..
>>>Not been there since it all went digital, now it is easy to store and delay one of more frames digitally...
>>>In the sixties we went color and look up Ampex 'amtec' and 'colortec', basically variable delay lines,
>>>the first to adjust the horizontal sync and the second to adjust the color carrier phase for signals coming from video tape
>>>recorders.
>>>There were many of those and ALL needed to be in sync to nano seconds (a few degrees of the 4.43MHz carrier) at the control
>>>panel so they could cross fade
>>>and that sync, for PAL takes several frames as it flips phase every frame,
>>>For 2 degrees color error at 4.43 MHz time error is  (1 / 4.43e6) / 180 = 1.25408e-09 say about 1.3 nS from any remote location
>>>/ video source (tape recorder for example).
>>>Even more so for the US NTSC system (short for Never Twice The Same Color as the joke goes), PAL did compensate for small phase
>>>/ color differences using a delay line.)
>>>sixties.....
>>>Anyways such a remote steering system compensates for any path delays dynamically and has proved itself.
>>>
>>>
>>>
>>
>>There is a pretty little town north of I80 in eastern California
>>called Grass Valley. It was the place where the Grass Valley Group
>>started and has become a mini-Silicon Valley.
>>
>>https://en.wikipedia.org/wiki/Grass_Valley,_California
>
>Seems it can get very hot there, litte rain also in summer.
>We just had a severe storm, and it has been raining for days.. Glad my satellite dish is still aligned.
>

We get no rain all summer here on the left coast, but it's cool and
fairly humid. In the sierra foothills, it's dry and warmer in the
summer with an occasional thunderstorm. That is of course a forest
fire weather pattern.

In the winter, starting about now, we'll get rain on the coast and
they'll get snow, 80 feet of snow around the sierra peak in a good
year.


>
>>https://en.wikipedia.org/wiki/Grass_Valley_(company)
>>
>>I think they pioneered digital video storage and resyncing.
>
>Things move fast in that field, lots is possible with ever more powerful electronics.
>
>When I left TV in 1976 or so we had equipment from Fernseh Gmbh: 
> https://en.m.wikipedia.org/wiki/Fernseh
>and Ampex., also color cameras from Philips (plumbican based)..
>Ampex quadruplex video tape recorders did cost millions...
>Been to Ampex for traning a few times.
>
>Now with digital electronics things can be much smaller and cheaper, solid state camera sensors.
>Anybody can start a TV studio with little money.
>
>Youtube an example, some channels have millions of viewers..
>
>
>>It's appealing, high technology in a small town the Sierra foothills.
>
>It's a moving target, very interesting.
>
>I am into music now, playing the keyboard...
>Select trumpet, play 'Moon river' 
>in the sixties I had a real trumpet, keyboards is different..


I don't like music, but that's just the way I'm wired.


>
>Thinking about making a big OLED or e-ink paper touch display for the notes.
>

On a sunny day (Fri, 03 Nov 2023 07:32:12 -0700) it happened John Larkin
<jl@997PotHill.com> wrote in <1l0akipp3mla2hoqh3i04vd9njp41onrat@4ax.com>:

>On Fri, 03 Nov 2023 05:22:04 GMT, Jan Panteltje <alien@comet.invalid>
>wrote:
>
>>On a sunny day (Thu, 02 Nov 2023 07:39:42 -0700) it happened John Larkin
>><jl@997PotHill.com> wrote in <snc7ki56n28ua94ck0hg20906kg0oejvi4@4ax.com>:
>>
>>>On Thu, 02 Nov 2023 04:16:52 GMT, Jan Panteltje <alien@comet.invalid>
>>>wrote:
>>>
>>>>On a sunny day (Wed, 01 Nov 2023 07:56:13 -0700) it happened John Larkin
>>>><jl@997PotHill.com> wrote in <0cp4ki1ui592aul2674qhmk85de16s8c3a@4ax.com>:
>>>>
>>>>
>>>>>Here's a paper about the NIF timing system.
>>>>>
>>>>>https://www.slac.stanford.edu/econf/C011127/TUAP069.pdf
>>>>>
>>>>>The biggest error is the prop delay tempco of the fiberoptics, around
>>>>>15 PPM/degC. The facility is BIG.
>>>>>
>>>>>https://en.wikipedia.org/wiki/National_Ignition_Facility
>>>>>
>>>>>I don't expect that laser fusion will ever be a practical power
>>>>>source. NIF is actually mainly for weapons research.
>>>>
>>>>Thank you for the links.
>>>>
>>>>Billions of dollars it did cost I read...
>>>>And the management knew it was crap...
>>>
>>>It's expensive but it works for the untended uses. It cost a fraction
>>>of ISS and some other things I could name.
>>>
>>>>Example of the US Military Industrial Complex.
>>>
>>>One use is to keep a number of researchers busy understanding the
>>>dynamics of nuclear weapons, refining simulations, now that we can't
>>>test them any more.
>>>
>>>One thing I have noticed is that the big-science and space programs
>>>seem to deliberately seek out small businesses as suppliers, and take
>>>a chance on them.
>>
>>Sure, some new ideas can come in handy.
>>
>>
>>>>
>>>>As to fusion power, I am not even sure ITER will work this time...
>>>>Probably needs to be rebuild a little bigger :-)
>>>>
>>>>Politics, job creation...
>>>
>>>Inefficient, but has at least some upside. I could name more expensive
>>>programs that are flat destructive.
>>
>>Fighting climate change :-) ?
>>
>>
>>As to timing, and I remember we discussed this before many years ago,
>>in the sixties in the TV studio where I had to keep things running, it was all about timing.
>>Mostly tubes in that old studio, some transistors.
>>When a video link from a remote location was used
>>it needed to be precisely in sync with the studio so they could cross-fade.
>>So you have a complex in time signal, vertical interval, horizontal sync, color burst and for color 4.43 MHz here.
>>To get things in sync we send carrier via one of the FM radio stations back to the remote location
>>that steered their clock generator until both frame and horizontal sync were aligned at out place.
>>Then we could cross-fade.
>>As you likely need sync at only one point, where the laser beams hit, one could use a low power laser and a detector
>>and use a complex signal that could be compared to adjust any remote electronics so the pulses at the 'blast'
>>place would be guaranteed to be in sync.
>>Fifties, sixties..
>>Not been there since it all went digital, now it is easy to store and delay one of more frames digitally...
>>In the sixties we went color and look up Ampex 'amtec' and 'colortec', basically variable delay lines,
>>the first to adjust the horizontal sync and the second to adjust the color carrier phase for signals coming from video tape
>>recorders.
>>There were many of those and ALL needed to be in sync to nano seconds (a few degrees of the 4.43MHz carrier) at the control
>>panel so they could cross fade
>>and that sync, for PAL takes several frames as it flips phase every frame,
>>For 2 degrees color error at 4.43 MHz time error is  (1 / 4.43e6) / 180 = 1.25408e-09 say about 1.3 nS from any remote location
>>/ video source (tape recorder for example).
>>Even more so for the US NTSC system (short for Never Twice The Same Color as the joke goes), PAL did compensate for small phase
>>/ color differences using a delay line.)
>>sixties.....
>>Anyways such a remote steering system compensates for any path delays dynamically and has proved itself.
>>
>>
>>
>
>There is a pretty little town north of I80 in eastern California
>called Grass Valley. It was the place where the Grass Valley Group
>started and has become a mini-Silicon Valley.
>
>https://en.wikipedia.org/wiki/Grass_Valley,_California

Seems it can get very hot there, litte rain also in summer.
We just had a severe storm, and it has been raining for days.. Glad my satellite dish is still aligned.


>https://en.wikipedia.org/wiki/Grass_Valley_(company)
>
>I think they pioneered digital video storage and resyncing.

Things move fast in that field, lots is possible with ever more powerful electronics.

When I left TV in 1976 or so we had equipment from Fernseh Gmbh: 
 https://en.m.wikipedia.org/wiki/Fernseh
and Ampex., also color cameras from Philips (plumbican based)..
Ampex quadruplex video tape recorders did cost millions...
Been to Ampex for traning a few times.

Now with digital electronics things can be much smaller and cheaper, solid state camera sensors.
Anybody can start a TV studio with little money.

Youtube an example, some channels have millions of viewers..


>It's appealing, high technology in a small town the Sierra foothills.

It's a moving target, very interesting.

I am into music now, playing the keyboard...
Select trumpet, play 'Moon river' 
in the sixties I had a real trumpet, keyboards is different..

Thinking about making a big OLED or e-ink paper touch display for the notes.


>
>
>
>
>
>>
>> 
>

On Saturday, November 4, 2023 at 1:32:49&#8239;AM UTC+11, John Larkin wrote:
> On Fri, 03 Nov 2023 05:22:04 GMT, Jan Panteltje <al...@comet.invalid>wrote: 
> >On a sunny day (Thu, 02 Nov 2023 07:39:42 -0700) it happened John Larkin <j...@997PotHill.com> wrote in <snc7ki56n28ua94ck...@4ax.com>: 
> >>On Thu, 02 Nov 2023 04:16:52 GMT, Jan Panteltje <al...@comet.invalid> wrote: 
> >>>On a sunny day (Wed, 01 Nov 2023 07:56:13 -0700) it happened John Larkin <j...@997PotHill.com> wrote in <0cp4ki1ui592aul26...@4ax.com>: 

<snip>

> There is a pretty little town north of I80 in eastern California  called Grass Valley. It was the place where the Grass Valley Group  started and has become a mini-Silicon Valley. 
> 
> https://en.wikipedia.org/wiki/Grass_Valley,_California 
> 
> https://en.wikipedia.org/wiki/Grass_Valley_(company) 
> 
> I think they pioneered digital video storage and resyncing. 
> 
> It's appealing, high technology in a small town the Sierra foothills. 

Grass_Valley got bought up by Terry Gooding at one point. He's a vulture capitalist - he bought up sick companies and ran them into the ground while extracting as much money as he could.

https://www.legacy.com/us/obituaries/sandiegouniontribune/name/terence-gooding-obituary?id=51627580

He owned Cambridge Instruments when I worked for it. The "high technology" involved is stinking carrion - except that the technology works, even if the corporate structure doesn't.

-- 
Bill Sloman, Sydney

On Fri, 03 Nov 2023 05:22:04 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

>On a sunny day (Thu, 02 Nov 2023 07:39:42 -0700) it happened John Larkin
><jl@997PotHill.com> wrote in <snc7ki56n28ua94ck0hg20906kg0oejvi4@4ax.com>:
>
>>On Thu, 02 Nov 2023 04:16:52 GMT, Jan Panteltje <alien@comet.invalid>
>>wrote:
>>
>>>On a sunny day (Wed, 01 Nov 2023 07:56:13 -0700) it happened John Larkin
>>><jl@997PotHill.com> wrote in <0cp4ki1ui592aul2674qhmk85de16s8c3a@4ax.com>:
>>>
>>>
>>>>Here's a paper about the NIF timing system.
>>>>
>>>>https://www.slac.stanford.edu/econf/C011127/TUAP069.pdf
>>>>
>>>>The biggest error is the prop delay tempco of the fiberoptics, around
>>>>15 PPM/degC. The facility is BIG.
>>>>
>>>>https://en.wikipedia.org/wiki/National_Ignition_Facility
>>>>
>>>>I don't expect that laser fusion will ever be a practical power
>>>>source. NIF is actually mainly for weapons research.
>>>
>>>Thank you for the links.
>>>
>>>Billions of dollars it did cost I read...
>>>And the management knew it was crap...
>>
>>It's expensive but it works for the untended uses. It cost a fraction
>>of ISS and some other things I could name.
>>
>>>Example of the US Military Industrial Complex.
>>
>>One use is to keep a number of researchers busy understanding the
>>dynamics of nuclear weapons, refining simulations, now that we can't
>>test them any more.
>>
>>One thing I have noticed is that the big-science and space programs
>>seem to deliberately seek out small businesses as suppliers, and take
>>a chance on them.
>
>Sure, some new ideas can come in handy.
>
>
>>>
>>>As to fusion power, I am not even sure ITER will work this time...
>>>Probably needs to be rebuild a little bigger :-)
>>>
>>>Politics, job creation...
>>
>>Inefficient, but has at least some upside. I could name more expensive
>>programs that are flat destructive.
>
>Fighting climate change :-) ?
>
>
>As to timing, and I remember we discussed this before many years ago,
>in the sixties in the TV studio where I had to keep things running, it was all about timing.
>Mostly tubes in that old studio, some transistors.
>When a video link from a remote location was used
>it needed to be precisely in sync with the studio so they could cross-fade.
>So you have a complex in time signal, vertical interval, horizontal sync, color burst and for color 4.43 MHz here.
>To get things in sync we send carrier via one of the FM radio stations back to the remote location
>that steered their clock generator until both frame and horizontal sync were aligned at out place.
>Then we could cross-fade.
>As you likely need sync at only one point, where the laser beams hit, one could use a low power laser and a detector
>and use a complex signal that could be compared to adjust any remote electronics so the pulses at the 'blast'
>place would be guaranteed to be in sync.
>Fifties, sixties..
>Not been there since it all went digital, now it is easy to store and delay one of more frames digitally...
>In the sixties we went color and look up Ampex 'amtec' and 'colortec', basically variable delay lines,
>the first to adjust the horizontal sync and the second to adjust the color carrier phase for signals coming from video tape recorders.
>There were many of those and ALL needed to be in sync to nano seconds (a few degrees of the 4.43MHz carrier) at the control panel so they could cross fade
>and that sync, for PAL takes several frames as it flips phase every frame,
>For 2 degrees color error at 4.43 MHz time error is  (1 / 4.43e6) / 180 = 1.25408e-09 say about 1.3 nS from any remote location / video source (tape recorder for example).
>Even more so for the US NTSC system (short for Never Twice The Same Color as the joke goes), PAL did compensate for small phase / color differences using a delay line.)
>sixties.....
>Anyways such a remote steering system compensates for any path delays dynamically and has proved itself.
>
>
>

There is a pretty little town north of I80 in eastern California
called Grass Valley. It was the place where the Grass Valley Group
started and has become a mini-Silicon Valley.

https://en.wikipedia.org/wiki/Grass_Valley,_California

https://en.wikipedia.org/wiki/Grass_Valley_(company)

I think they pioneered digital video storage and resyncing.

It's appealing, high technology in a small town the Sierra foothills.







>
>

On Friday, November 3, 2023 at 4:22:13&#8239;PM UTC+11, Jan Panteltje wrote:
> On a sunny day (Thu, 02 Nov 2023 07:39:42 -0700) it happened John Larkin 
> <j...@997PotHill.com> wrote in <snc7ki56n28ua94ck...@4ax.com>:
> >On Thu, 02 Nov 2023 04:16:52 GMT, Jan Panteltje <al...@comet.invalid> 
> >wrote: 
> > 
> >>On a sunny day (Wed, 01 Nov 2023 07:56:13 -0700) it happened John Larkin 
> >><j...@997PotHill.com> wrote in <0cp4ki1ui592aul26...@4ax.com>: 
> >> 
> >> 
> >>>Here's a paper about the NIF timing system. 
> >>> 
> >>>https://www.slac.stanford.edu/econf/C011127/TUAP069.pdf 
> >>> 
> >>>The biggest error is the prop delay tempco of the fiberoptics, around 
> >>>15 PPM/degC. The facility is BIG. 
> >>> 
> >>>https://en.wikipedia.org/wiki/National_Ignition_Facility 
> >>> 
> >>>I don't expect that laser fusion will ever be a practical power 
> >>>source. NIF is actually mainly for weapons research. 
> >> 
> >>Thank you for the links. 
> >> 
> >>Billions of dollars it did cost I read... 
> >>And the management knew it was crap... 
> > 
> >It's expensive but it works for the untended uses. It cost a fraction 
> >of ISS and some other things I could name. 
> > 
> >>Example of the US Military Industrial Complex. 
> > 
> >One use is to keep a number of researchers busy understanding the 
> >dynamics of nuclear weapons, refining simulations, now that we can't 
> >test them any more. 
> > 
> >One thing I have noticed is that the big-science and space programs 
> >seem to deliberately seek out small businesses as suppliers, and take 
> >a chance on them.
>
> Sure, some new ideas can come in handy.

But John Larkin's time delay for the NIF was a reworking of HP's effort from 1978 - not any kind of new idea - and it's not the approach I came up with in 1988 when fast eight-bit ADCs and DACs had made a better approach practical. More  a case of a legacy designer pushing a old idea further than strikes me as wise.

> >>As to fusion power, I am not even sure ITER will work this time... 
> >>Probably needs to be rebuild a little bigger :-) 
> >> 
> >>Politics, job creation... 
> > 
> >Inefficient, but has at least some upside. I could name more expensive programs that are flat destructive.
>
> Fighting climate change :-) ? 

John Larkin is a gullible sucker for climate change denial propaganda. so perhaps he might see it that way.
Cursitor Doom likes his nonsense to be utterly absurd. Maybe John Larkin shares this preference to some extent.

-- 
Bill Sloman,  Sydney

On a sunny day (Thu, 02 Nov 2023 07:39:42 -0700) it happened John Larkin
<jl@997PotHill.com> wrote in <snc7ki56n28ua94ck0hg20906kg0oejvi4@4ax.com>:

>On Thu, 02 Nov 2023 04:16:52 GMT, Jan Panteltje <alien@comet.invalid>
>wrote:
>
>>On a sunny day (Wed, 01 Nov 2023 07:56:13 -0700) it happened John Larkin
>><jl@997PotHill.com> wrote in <0cp4ki1ui592aul2674qhmk85de16s8c3a@4ax.com>:
>>
>>
>>>Here's a paper about the NIF timing system.
>>>
>>>https://www.slac.stanford.edu/econf/C011127/TUAP069.pdf
>>>
>>>The biggest error is the prop delay tempco of the fiberoptics, around
>>>15 PPM/degC. The facility is BIG.
>>>
>>>https://en.wikipedia.org/wiki/National_Ignition_Facility
>>>
>>>I don't expect that laser fusion will ever be a practical power
>>>source. NIF is actually mainly for weapons research.
>>
>>Thank you for the links.
>>
>>Billions of dollars it did cost I read...
>>And the management knew it was crap...
>
>It's expensive but it works for the untended uses. It cost a fraction
>of ISS and some other things I could name.
>
>>Example of the US Military Industrial Complex.
>
>One use is to keep a number of researchers busy understanding the
>dynamics of nuclear weapons, refining simulations, now that we can't
>test them any more.
>
>One thing I have noticed is that the big-science and space programs
>seem to deliberately seek out small businesses as suppliers, and take
>a chance on them.

Sure, some new ideas can come in handy.

>>
>>As to fusion power, I am not even sure ITER will work this time...
>>Probably needs to be rebuild a little bigger :-)
>>
>>Politics, job creation...
>
>Inefficient, but has at least some upside. I could name more expensive
>programs that are flat destructive.

Fighting climate change :-) ?

As to timing, and I remember we discussed this before many years ago,
in the sixties in the TV studio where I had to keep things running, it was all about timing.
Mostly tubes in that old studio, some transistors.
When a video link from a remote location was used
it needed to be precisely in sync with the studio so they could cross-fade.
So you have a complex in time signal, vertical interval, horizontal sync, color burst and for color 4.43 MHz here.
To get things in sync we send carrier via one of the FM radio stations back to the remote location
that steered their clock generator until both frame and horizontal sync were aligned at out place.
Then we could cross-fade.
As you likely need sync at only one point, where the laser beams hit, one could use a low power laser and a detector
and use a complex signal that could be compared to adjust any remote electronics so the pulses at the 'blast'
place would be guaranteed to be in sync.
Fifties, sixties..
Not been there since it all went digital, now it is easy to store and delay one of more frames digitally...
In the sixties we went color and look up Ampex 'amtec' and 'colortec', basically variable delay lines,
the first to adjust the horizontal sync and the second to adjust the color carrier phase for signals coming from video tape recorders.
There were many of those and ALL needed to be in sync to nano seconds (a few degrees of the 4.43MHz carrier) at the control panel so they could cross fade
and that sync, for PAL takes several frames as it flips phase every frame,
For 2 degrees color error at 4.43 MHz time error is  (1 / 4.43e6) / 180 = 1.25408e-09 say about 1.3 nS from any remote location / video source (tape recorder for example).
Even more so for the US NTSC system (short for Never Twice The Same Color as the joke goes), PAL did compensate for small phase / color differences using a delay line.)
sixties.....
Anyways such a remote steering system compensates for any path delays dynamically and has proved itself.