Am 27.07.22 um 10:36 schrieb Martin Brown:
> On 26/07/2022 13:05, Phil Hobbs wrote:
>> Gerhard Hoffmann wrote:
>>> Am 25.07.22 um 18:31 schrieb Joe Gwinn:
>>>> On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs

> Entrainment of weakly coupled oscillators at frequencies near to each
> other can be quite strong (a problem if you don't want that to happen).

But I want to lock them to the same frequency and phase anyway
with dedicated slooow PLLs. Injection locking would just
take away some control over the corner frequencies of the PLLs.
As long as the corners a low enough that is not a desaster.
Say below 0.5 Hz.

I did not see that the 2 Morion MV89A oscillators I use as a
cross corr reference talk to each other. The double oven and
the hermetically soldered box probably help. And there is a
frequency doubler to the output.

> I think the catch is that to do that you would have to provide hardware
> to compute the cross correlation of every pair of oscillators so that
> correlator complexity goes up as N(N-1)/2 too. I can't immediately see a
> way to exploit this to get a better average oscillator though.

My Timepod can do the 3 cornered hat only. Since 2 corners are
already reserved for the X-Band extension, I cannot remove the
noise of the reference by cross correlation via the 2
independent oscillators.

But then, the X-Band sources are not that wonderful. It's not
necessary to swim faster than the sharc, It's enough to swim
faster than your neighbour.

BUT IT'S STILL FOR THE SPORTS!

Cheers,
Gerhard, DK4XP

On 2022-07-23, whit3rd <whit3rd@gmail.com> wrote:
> On Friday, July 22, 2022 at 2:38:45 PM UTC-7, Don wrote:
>> Joe Gwinn wrote:
>>
>> <snip>
>> > Also, I'd lose the BNC connectors. Threaded connectors like SMA, TNC,
>> > and Type N are far better.
>> >
>> > Or use shielded twisted pair to carry the 1PPS pulses.
>
>> Twisted pair (TP) sounds even easier than BNC. So, what's the
>> "catch" with TP? Where's the "gotcha" to make TP harder than BNC?
>
> Biggest 'gotcha' is the lack of good shielded TP connectors. I had only
> UHF-style twisted pair shielded connectors last time I wanted some, and
> that's a polarity-insensitive connector. We applied paint markings
> to get it straight.

> MiniDIN 3 (don't trust the shield connector) was what Apple used for their
> LocalTalk/Appletalk hardware,

SVHS ran a higher bandwidth, unbalanced, over the 4 pin version.
localtalk was only a few hundered kilobaud.

Shileded pair conectors are fairly common now, USB, HDMI, SATA all give
multiple shielded pairs. (SATA is actully untwisted). Oh shit! I
forgot "RJ45" is also used for STP.

--

Jasen.

On Tue, 26 Jul 2022 11:03:15 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>jlarkin@highlandsniptechnology.com wrote:
>> On Tue, 26 Jul 2022 08:05:49 -0400, Phil Hobbs
>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>
>>> Gerhard Hoffmann wrote:
>>>> Am 25.07.22 um 18:31 schrieb Joe Gwinn:
>>>>> On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs
>>>>
>>>>> "A geometric view of closure phases in interferometry", DOI:
>>>>> <https://doi.org/10.1017/pasa.2022.6>
>>>>>
>>>>> .<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7>
>>>>>
>>>>>
>>>>>
>>>>> I'm still digesting it, but basically deducing the underlying geometry
>>>>> allowed for some significant improvements.
>>>>
>>>> I have not yet digested it, but can I assume that it won't help
>>>> me to create a carrier that is phase noise wise better than
>>>> averaged over 16 oscillators created equally bad?
>>>>
>>>> More suitable for post-processing after-the-fact?
>>>>
>>>> U. Rohde has the math for n injection locked oscillators in one
>>>> of his books, but the formulas probably fall apart when you have
>>>> to insert hard numbers for real oscillators you can buy, or build.
>>>> Methinks he is more into multiple coupled resonators.
>>>>
>>>> cheers,
>>>> Gerhard
>>>
>>> I'm not sure--as I say, I haven't got a properly-thought-out scheme, but
>>> it seems as though it ought to be possible to combine the measurements
>>> to produce N-1 oscillator signals, each one N times quieter, so that
>>> averaging _those_ would get you to the N(N-1)/2 level.
>>>
>>> It probably needs a whole lot of phase shifters or weighted summers
>>> (like a Wilkinson with attenuators), so it may well not be a win from a
>>> total-hardware POV. Seems like it would be worth a bit of thought, though.
>>>
>>> Cheers
>>>
>>> Phil Hobbs
>>
>> Imagine a single circuit/pcb that has N crystal oscillator circuits,
>> injection locked and summed, in an oven.
>>
>> XOs near one another, namely in the same room, like to injection lock.
>
>Sure. That only gets you 10*log(N), though, AFAICT. Looking at it from
>a phase noise POV, you win improved <delta phi> like sqrt(N), just as
>you gain lower <delta V> by parallelling JFETs.
>
>Cheers
>
>Phil Hobbs

I'm beyond my pay grade here, but summing jfets can be done with an
ideal isolated n-port summer and the s/n improvement indeed goes as
sqrt(n). But injection locking 10 oscillators is different. Each one
pulls towards the mean of the other nine. They herd one another.

Martin Brown wrote:
> On 26/07/2022 13:05, Phil Hobbs wrote:
>> Gerhard Hoffmann wrote:
>>> Am 25.07.22 um 18:31 schrieb Joe Gwinn:
>>>> On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs
>>>
>>>> "A geometric view of closure phases in interferometry", DOI:
>>>> <https://doi.org/10.1017/pasa.2022.6>
>>>>
>>>> .<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7>
>>>>
>>>> I'm still digesting it, but basically deducing the underlying geometry
>>>> allowed for some significant improvements.
>>>
>>> I have not yet digested it, but can I assume that it won't help
>>> me to create a carrier that is phase noise wise better than
>>> averaged over 16 oscillators created equally bad?
>>>
>>> More suitable for post-processing after-the-fact?
>>>
>>> U. Rohde has the math for n injection locked oscillators in one
>>> of his books, but the formulas probably fall apart when you have
>>> to insert hard numbers for real oscillators you can buy, or build.
>>> Methinks he is more into multiple coupled resonators.
>
> Entrainment of weakly coupled oscillators at frequencies near to each
> other can be quite strong (a problem if you don't want that to happen).
>>
>> I'm not sure--as I say, I haven't got a properly-thought-out scheme,
>> but it seems as though it ought to be possible to combine the
>> measurements to produce N-1 oscillator signals, each one N times
>> quieter, so that averaging _those_ would get you to the N(N-1)/2 level.
>
> I think the catch is that to do that you would have to provide hardware
> to compute the cross correlation of every pair of oscillators so that
> correlator complexity goes up as N(N-1)/2 too. I can't immediately see a
> way to exploit this to get a better average oscillator though.
>>
>> It probably needs a whole lot of phase shifters or weighted summers
>> (like a Wilkinson with attenuators), so it may well not be a win from
>> a total-hardware POV.  Seems like it would be worth a bit of thought,
>> though.
>
> VLBI typically disciplines a hydrogen maser using some other long term
> stable centralised terrestrial time source. Getting it just a little bit
> wrong just makes the white light fringe much harder to find later. Local
> clock short term stability stability is the key to it working well.
>
> I expect they  are a lot better at it by now. In my day it involved
> moving around furniture van loads of tweaked VHS video tape cassettes
> from the big dishes to the correlator centres.

As the wise man said, "Never underestimate the bandwidth of a truck full
of tapes."

Also, variously, a 747 full of tapes, CDs, DVDs, MicroSDs, etc. A
747-load of 256-GB MicroSDs is about
256e12 B * 113,400 kg / 0.25 g = 1.16E+23 bytes.

Six of them would be over 1 Avogadro.

Of course reading them out in less than the lifetime of the universe
would take quite a few boxes--it would need a bandwidth of
1.16E+23 / 3.156e+7 / 15e+9 = 245 kB/s just to do that.

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

jlarkin@highlandsniptechnology.com wrote:
> On Tue, 26 Jul 2022 11:03:15 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> jlarkin@highlandsniptechnology.com wrote:
>>> On Tue, 26 Jul 2022 08:05:49 -0400, Phil Hobbs
>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>
>>>> Gerhard Hoffmann wrote:
>>>>> Am 25.07.22 um 18:31 schrieb Joe Gwinn:
>>>>>> On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs
>>>>>
>>>>>> "A geometric view of closure phases in interferometry", DOI:
>>>>>> <https://doi.org/10.1017/pasa.2022.6>
>>>>>>
>>>>>> .<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7>
>>>>>>
>>>>>>
>>>>>>
>>>>>> I'm still digesting it, but basically deducing the underlying geometry
>>>>>> allowed for some significant improvements.
>>>>>
>>>>> I have not yet digested it, but can I assume that it won't help
>>>>> me to create a carrier that is phase noise wise better than
>>>>> averaged over 16 oscillators created equally bad?
>>>>>
>>>>> More suitable for post-processing after-the-fact?
>>>>>
>>>>> U. Rohde has the math for n injection locked oscillators in one
>>>>> of his books, but the formulas probably fall apart when you have
>>>>> to insert hard numbers for real oscillators you can buy, or build.
>>>>> Methinks he is more into multiple coupled resonators.
>>>>>
>>>>> cheers,
>>>>> Gerhard
>>>>
>>>> I'm not sure--as I say, I haven't got a properly-thought-out scheme, but
>>>> it seems as though it ought to be possible to combine the measurements
>>>> to produce N-1 oscillator signals, each one N times quieter, so that
>>>> averaging _those_ would get you to the N(N-1)/2 level.
>>>>
>>>> It probably needs a whole lot of phase shifters or weighted summers
>>>> (like a Wilkinson with attenuators), so it may well not be a win from a
>>>> total-hardware POV. Seems like it would be worth a bit of thought, though.
>>>>
>>>> Cheers
>>>>
>>>> Phil Hobbs
>>>
>>> Imagine a single circuit/pcb that has N crystal oscillator circuits,
>>> injection locked and summed, in an oven.
>>>
>>> XOs near one another, namely in the same room, like to injection lock.
>>
>> Sure. That only gets you 10*log(N), though, AFAICT. Looking at it from
>> a phase noise POV, you win improved <delta phi> like sqrt(N), just as
>> you gain lower <delta V> by parallelling JFETs.
>>
>> Cheers
>>
>> Phil Hobbs
>
> I'm beyond my pay grade here, but summing jfets can be done with an
> ideal isolated n-port summer and the s/n improvement indeed goes as
> sqrt(n). But injection locking 10 oscillators is different. Each one
> pulls towards the mean of the other nine. They herd one another.
>

Yup. Inside the locking bandwidth, it's probably possible to make the
phases chaotic at some level, so the close-in noise might even be worse.

Outside that, though, as long as the peak phase error is smallish, both
amplitude and phase noise look additive, so the usual theorems apply.

For small epsilon,

sin(t + epsilon) = sin t cos epsilon + cos t sin epsilon

~= sin t + epsilon*cos t, (1)

so

(sin(t) + sin(t + epsilon))/2 ~=

sin t + (epsilon / 2) cos t. (2)

Using (1) backwards,

(sin(t) + sin(t + epsilon))/2 ~= sin(t + epsilon / 2).

With N different epsilons, you have a random phasor sum, which winds up
with an average phase error going like 1/sqrt(N).

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 Wed, 27 Jul 2022 10:29:44 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>jlarkin@highlandsniptechnology.com wrote:
>> On Tue, 26 Jul 2022 11:03:15 -0400, Phil Hobbs
>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>
>>> jlarkin@highlandsniptechnology.com wrote:
>>>> On Tue, 26 Jul 2022 08:05:49 -0400, Phil Hobbs
>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>>
>>>>> Gerhard Hoffmann wrote:
>>>>>> Am 25.07.22 um 18:31 schrieb Joe Gwinn:
>>>>>>> On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs
>>>>>>
>>>>>>> "A geometric view of closure phases in interferometry", DOI:
>>>>>>> <https://doi.org/10.1017/pasa.2022.6>
>>>>>>>
>>>>>>> .<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> I'm still digesting it, but basically deducing the underlying geometry
>>>>>>> allowed for some significant improvements.
>>>>>>
>>>>>> I have not yet digested it, but can I assume that it won't help
>>>>>> me to create a carrier that is phase noise wise better than
>>>>>> averaged over 16 oscillators created equally bad?
>>>>>>
>>>>>> More suitable for post-processing after-the-fact?
>>>>>>
>>>>>> U. Rohde has the math for n injection locked oscillators in one
>>>>>> of his books, but the formulas probably fall apart when you have
>>>>>> to insert hard numbers for real oscillators you can buy, or build.
>>>>>> Methinks he is more into multiple coupled resonators.
>>>>>>
>>>>>> cheers,
>>>>>> Gerhard
>>>>>
>>>>> I'm not sure--as I say, I haven't got a properly-thought-out scheme, but
>>>>> it seems as though it ought to be possible to combine the measurements
>>>>> to produce N-1 oscillator signals, each one N times quieter, so that
>>>>> averaging _those_ would get you to the N(N-1)/2 level.
>>>>>
>>>>> It probably needs a whole lot of phase shifters or weighted summers
>>>>> (like a Wilkinson with attenuators), so it may well not be a win from a
>>>>> total-hardware POV. Seems like it would be worth a bit of thought, though.
>>>>>
>>>>> Cheers
>>>>>
>>>>> Phil Hobbs
>>>>
>>>> Imagine a single circuit/pcb that has N crystal oscillator circuits,
>>>> injection locked and summed, in an oven.
>>>>
>>>> XOs near one another, namely in the same room, like to injection lock.
>>>
>>> Sure. That only gets you 10*log(N), though, AFAICT. Looking at it from
>>> a phase noise POV, you win improved <delta phi> like sqrt(N), just as
>>> you gain lower <delta V> by parallelling JFETs.
>>>
>>> Cheers
>>>
>>> Phil Hobbs
>>
>> I'm beyond my pay grade here, but summing jfets can be done with an
>> ideal isolated n-port summer and the s/n improvement indeed goes as
>> sqrt(n). But injection locking 10 oscillators is different. Each one
>> pulls towards the mean of the other nine. They herd one another.
>>
>
>Yup. Inside the locking bandwidth, it's probably possible to make the
>phases chaotic at some level, so the close-in noise might even be worse.
>
>Outside that, though, as long as the peak phase error is smallish, both
>amplitude and phase noise look additive, so the usual theorems apply.
>
>For small epsilon,
>
>sin(t + epsilon) = sin t cos epsilon + cos t sin epsilon
>
>~= sin t + epsilon*cos t, (1)
>
>so
>
>(sin(t) + sin(t + epsilon))/2 ~=
>
>sin t + (epsilon / 2) cos t. (2)
>
>
>Using (1) backwards,
>
>(sin(t) + sin(t + epsilon))/2 ~= sin(t + epsilon / 2).
>
>With N different epsilons, you have a random phasor sum, which winds up
>with an average phase error going like 1/sqrt(N).
>
>Cheers
>
>Phil Hobbs

Of course the summing follows the usual linear equations AFTER the
oscillators are locked. But the things being summed are changed by the
phase locking, not independent sources any more.

If one oscillator is the big outlier, it gets all nine others pounding
on it to get in sync. Injection locking is fundamentally nonlinear.

On a sunny day (Wed, 27 Jul 2022 12:12:42 +0200) it happened Gerhard Hoffmann
<dk4xp@arcor.de> wrote in <tbr32q$qg7c$1@solani.org>:

>Am 27.07.22 um 10:36 schrieb Martin Brown:
>> On 26/07/2022 13:05, Phil Hobbs wrote:
>>> Gerhard Hoffmann wrote:
>>>> Am 25.07.22 um 18:31 schrieb Joe Gwinn:
>>>>> On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs
>
>
>> Entrainment of weakly coupled oscillators at frequencies near to each
>> other can be quite strong (a problem if you don't want that to happen).
>
>But I want to lock them to the same frequency and phase anyway
>with dedicated slooow PLLs. Injection locking would just
>take away some control over the corner frequencies of the PLLs.
>As long as the corners a low enough that is not a desaster.
>Say below 0.5 Hz.

No idea what you are doing, but in the old days of Ampex broadcast videotape
recorders there were several loops on top of each other to get the color carrier to nano seconds precision in playback
1) slow one capstan tape speed
2) 4 head rotating scanning head to get the signal from tape
3) AMTEC (Automatic Time Element Compensator) a variable delay to get the video to micro second correct phase
4) Colortec a vaiable delay to sync the playback 4.43 MHz playback color carrier to the studio precision reference
all this so they could cross-fade and edit and use effects, and people's TVs would sync. and display color.

Old tech...
Slow PLL was not the way it worked,
From tape speed variations to nano second precision.
google Ampex AMTEC and Ampex Colortec
sixties and seventies

Am 27.07.22 um 16:13 schrieb Phil Hobbs:

>> I expect they  are a lot better at it by now. In my day it involved
>> moving around furniture van loads of tweaked VHS video tape cassettes
>> from the big dishes to the correlator centres.
>
> As the wise man said, "Never underestimate the bandwidth of a truck full
> of tapes."

That was Andy Tanenbaum, either in his book "Structured Computer
Organisation" or in a guest lecture i saw at TU Berlin.
I was seldom more impressed by a prof.

He announced the "Free Univerity Compiler Kit", from the
Free Univerity Amsterdam. :-)

Gerhard

Am 27.07.22 um 18:13 schrieb Gerhard Hoffmann:

> He announced the "Free Univerity Compiler Kit", from the
> Free Univerity Amsterdam.  :-)

:gs/Univerity/University/

I hate that keyboard.

> Gerhard

Am 27.07.22 um 17:00 schrieb jlarkin@highlandsniptechnology.com:

> Of course the summing follows the usual linear equations AFTER the
> oscillators are locked. But the things being summed are changed by the
> phase locking, not independent sources any more.
>
> If one oscillator is the big outlier, it gets all nine others pounding
> on it to get in sync. Injection locking is fundamentally nonlinear.
>
No, they all follow the Lucent GPS timing receiver and its own MTI-260
oven by a dedicated PLL in my case

Les Cargill wrote:
> jlarkin@highlandsniptechnology.com wrote:
>> Les Cargill wrote:
>>> jlarkin@highlandsniptechnology.com wrote:
>>>> Phil Hobbs wrote:
>>> <snip>
>>>>> Phil Hobbs
>>>>
>>>> Mathematicians often like music. In my experience, music fandom is
>>>> negatively correlated to engineering design skill. Different brain
>>>> structure or something.
>>>
>>> Engineering is composition. Composition is the thin edge of the musical
>>> wedge. Musicianship is different; it's pattern identification. As is
>>> composition but in a different way. But it is all the same thing.
>>>
>>> It all depends on which wall you prefer to have your back against.
>>
>> I've always wondered about musicians. They have to play a piece
>> hundreds of times to get it right.
>
> Some do; some don't. Session players from back when studio time
> was the dominant cost probably played the parts on a song you later
> heard on the radio on the first take.
>
>> Some have surely performed
>> something thousands of times. Don't they get bored? Apparently not.
>>
>
> There's too broad a spectrum to generalize. Some forms are better for
> people with mild forms of OCD.
>
>> I design something, finish, and then want to design something entirely
>> different.
>>
>> It depends on boredom thresholds.
>>
>
> Much does.

<snip>

My much older, late partner used to play saxophone in High School in the
1950s. He belonged to an Illinois union and said you had to sight read
sheet music to join the union.
It was the big band era. To keep costs down, the band's core, of say
six musicians, would tour and then hire local union musicians for a one
night stand in order to fill out the big band.

There's a Muscle Shoals studio interview somewhere out on the Inet. In
it one of the sessions players talks about how he played by ear - at
first. Until someone told him he needed to wise-up and learn how to
sight read in order to earn the easiest money.

My church's two volume songbook contains 634 songs. And a different mix
is played each weekend. It's best to simply sight read the songs, as
needed.

Humble symphony orchestras work it about the same. Part-time musicians
pick up their sheet music a day or two before a concert. There's simply
not enough available time to "play a piece hundreds of times to get it
right."

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

jlarkin@highlandsniptechnology.com wrote:
> On Wed, 27 Jul 2022 10:29:44 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> jlarkin@highlandsniptechnology.com wrote:
>>> On Tue, 26 Jul 2022 11:03:15 -0400, Phil Hobbs
>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>
>>>> jlarkin@highlandsniptechnology.com wrote:
>>>>> On Tue, 26 Jul 2022 08:05:49 -0400, Phil Hobbs
>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>>>
>>>>>> Gerhard Hoffmann wrote:
>>>>>>> Am 25.07.22 um 18:31 schrieb Joe Gwinn:
>>>>>>>> On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs
>>>>>>>
>>>>>>>> "A geometric view of closure phases in interferometry", DOI:
>>>>>>>> <https://doi.org/10.1017/pasa.2022.6>
>>>>>>>>
>>>>>>>> .<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> I'm still digesting it, but basically deducing the underlying geometry
>>>>>>>> allowed for some significant improvements.
>>>>>>>
>>>>>>> I have not yet digested it, but can I assume that it won't help
>>>>>>> me to create a carrier that is phase noise wise better than
>>>>>>> averaged over 16 oscillators created equally bad?
>>>>>>>
>>>>>>> More suitable for post-processing after-the-fact?
>>>>>>>
>>>>>>> U. Rohde has the math for n injection locked oscillators in one
>>>>>>> of his books, but the formulas probably fall apart when you have
>>>>>>> to insert hard numbers for real oscillators you can buy, or build.
>>>>>>> Methinks he is more into multiple coupled resonators.
>>>>>>>
>>>>>>> cheers,
>>>>>>> Gerhard
>>>>>>
>>>>>> I'm not sure--as I say, I haven't got a properly-thought-out scheme, but
>>>>>> it seems as though it ought to be possible to combine the measurements
>>>>>> to produce N-1 oscillator signals, each one N times quieter, so that
>>>>>> averaging _those_ would get you to the N(N-1)/2 level.
>>>>>>
>>>>>> It probably needs a whole lot of phase shifters or weighted summers
>>>>>> (like a Wilkinson with attenuators), so it may well not be a win from a
>>>>>> total-hardware POV. Seems like it would be worth a bit of thought, though.
>>>>>>
>>>>>> Cheers
>>>>>>
>>>>>> Phil Hobbs
>>>>>
>>>>> Imagine a single circuit/pcb that has N crystal oscillator circuits,
>>>>> injection locked and summed, in an oven.
>>>>>
>>>>> XOs near one another, namely in the same room, like to injection lock.
>>>>
>>>> Sure. That only gets you 10*log(N), though, AFAICT. Looking at it from
>>>> a phase noise POV, you win improved <delta phi> like sqrt(N), just as
>>>> you gain lower <delta V> by parallelling JFETs.
>>>>
>>>> Cheers
>>>>
>>>> Phil Hobbs
>>>
>>> I'm beyond my pay grade here, but summing jfets can be done with an
>>> ideal isolated n-port summer and the s/n improvement indeed goes as
>>> sqrt(n). But injection locking 10 oscillators is different. Each one
>>> pulls towards the mean of the other nine. They herd one another.
>>>
>>
>> Yup. Inside the locking bandwidth, it's probably possible to make the
>> phases chaotic at some level, so the close-in noise might even be worse.
>>
>> Outside that, though, as long as the peak phase error is smallish, both
>> amplitude and phase noise look additive, so the usual theorems apply.
>>
>> For small epsilon,
>>
>> sin(t + epsilon) = sin t cos epsilon + cos t sin epsilon
>>
>> ~= sin t + epsilon*cos t, (1)
>>
>> so
>>
>> (sin(t) + sin(t + epsilon))/2 ~=
>>
>> sin t + (epsilon / 2) cos t. (2)
>>
>>
>> Using (1) backwards,
>>
>> (sin(t) + sin(t + epsilon))/2 ~= sin(t + epsilon / 2).
>>
>> With N different epsilons, you have a random phasor sum, which winds up
>> with an average phase error going like 1/sqrt(N).
>>

>
> Of course the summing follows the usual linear equations AFTER the
> oscillators are locked. But the things being summed are changed by the
> phase locking, not independent sources any more.

Well outside the lock bandwidth, they'd be pretty well independent, I
should think.

> If one oscillator is the big outlier, it gets all nine others pounding
> on it to get in sync. Injection locking is fundamentally nonlinear.

Yes, and the math is very pretty, as I remember--all sorts of
bifurcations and strange attractors and limit cycles and stuff. It gets
more boring with weaker coupling, which is usually all you need.

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

Gerhard Hoffmann wrote:
> Am 27.07.22 um 16:13 schrieb Phil Hobbs:
>
>>> I expect they  are a lot better at it by now. In my day it involved
>>> moving around furniture van loads of tweaked VHS video tape cassettes
>>> from the big dishes to the correlator centres.
>>
>> As the wise man said, "Never underestimate the bandwidth of a truck
>> full of tapes."
>
> That was Andy Tanenbaum, either in his book "Structured Computer
> Organisation" or in a guest lecture i saw at TU Berlin.
> I was seldom more impressed by a prof.
>
> He announced the "Free Univerity Compiler Kit", from the
> Free Univerity Amsterdam.  :-)

Well, after all, it's more prestigious than the South Holland Institute
of Technology.

Cheers

Phil Hobbs

On Wed, 27 Jul 2022 10:13:21 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>Martin Brown wrote:
>> On 26/07/2022 13:05, Phil Hobbs wrote:
>>> Gerhard Hoffmann wrote:
>>>> Am 25.07.22 um 18:31 schrieb Joe Gwinn:
>>>>> On Fri, 22 Jul 2022 09:03:16 -0400, Phil Hobbs
>>>>
>>>>> "A geometric view of closure phases in interferometry", DOI:
>>>>> <https://doi.org/10.1017/pasa.2022.6>
>>>>>
>>>>> .<https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/geometric-view-of-closure-phases-in-interferometry/5E8A5A8D58A2FC72ADFA0587347C4DA7>
>>>>>
>>>>> I'm still digesting it, but basically deducing the underlying geometry
>>>>> allowed for some significant improvements.
>>>>
>>>> I have not yet digested it, but can I assume that it won't help
>>>> me to create a carrier that is phase noise wise better than
>>>> averaged over 16 oscillators created equally bad?
>>>>
>>>> More suitable for post-processing after-the-fact?
>>>>
>>>> U. Rohde has the math for n injection locked oscillators in one
>>>> of his books, but the formulas probably fall apart when you have
>>>> to insert hard numbers for real oscillators you can buy, or build.
>>>> Methinks he is more into multiple coupled resonators.
>>
>> Entrainment of weakly coupled oscillators at frequencies near to each
>> other can be quite strong (a problem if you don't want that to happen).
>>>
>>> I'm not sure--as I say, I haven't got a properly-thought-out scheme,
>>> but it seems as though it ought to be possible to combine the
>>> measurements to produce N-1 oscillator signals, each one N times
>>> quieter, so that averaging _those_ would get you to the N(N-1)/2 level.
>>
>> I think the catch is that to do that you would have to provide hardware
>> to compute the cross correlation of every pair of oscillators so that
>> correlator complexity goes up as N(N-1)/2 too. I can't immediately see a
>> way to exploit this to get a better average oscillator though.
>>>
>>> It probably needs a whole lot of phase shifters or weighted summers
>>> (like a Wilkinson with attenuators), so it may well not be a win from
>>> a total-hardware POV.  Seems like it would be worth a bit of thought,
>>> though.
>>
>> VLBI typically disciplines a hydrogen maser using some other long term
>> stable centralised terrestrial time source. Getting it just a little bit
>> wrong just makes the white light fringe much harder to find later. Local
>> clock short term stability stability is the key to it working well.
>>
>> I expect they  are a lot better at it by now. In my day it involved
>> moving around furniture van loads of tweaked VHS video tape cassettes
>> from the big dishes to the correlator centres.
>
>As the wise man said, "Never underestimate the bandwidth of a truck full
>of tapes."
>
>Also, variously, a 747 full of tapes, CDs, DVDs, MicroSDs, etc. A
>747-load of 256-GB MicroSDs is about
>256e12 B * 113,400 kg / 0.25 g = 1.16E+23 bytes.
>
>Six of them would be over 1 Avogadro.
>
>Of course reading them out in less than the lifetime of the universe
>would take quite a few boxes--it would need a bandwidth of
>1.16E+23 / 3.156e+7 / 15e+9 = 245 kB/s just to do that.
>
>Cheers
>
>Phil Hobbs

I suspected that I've been taking too many pictures.

On Fri, 22 Jul 2022 21:12:31 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>Joe Gwinn wrote:
>> On Fri, 22 Jul 2022 21:38:39 -0000 (UTC), "Don" <g@crcomp.net> wrote:
>>
>>> Joe Gwinn wrote:
>>>
>>> <snip>
>>>
>>>> Also, I'd lose the BNC connectors. Threaded connectors like SMA, TNC,
>>>> and Type N are far better.
>>>>
>>>> Or use shielded twisted pair to carry the 1PPS pulses. This would
>>>> work better over a backplane.
>>>
>>> This is good advice. Even though the lazy guy within me never truly
>>> gives up his fight to take the easy way out with BNC.
>>> Twisted pair (TP) sounds even easier than BNC. So, what's the
>>> "catch" with TP? Where's the "gotcha" to make TP harder than BNC?
>>
>> Depends on what you are trying to do.
>>
>> For nanosecond edges, coax is pretty useful, but short range and often
>> mechanically awkward.
>>
>> For microsecond edges at 1000 meters, RS422 over shielded twisted pair
>> is pretty good.
>>
>> For bus length links, LVDS or the like.
>>
>> And so on. And there is always optical links.
>>
>> Joe Gwinn
>>
>
>BNCs are the bomb, as long as you aren't putting 500 of them in series,
>as with the old 10base2 coax Ethernet.
>
>TNCs are a very small niche, and N connectors belong only on spectrum
>analyzers.

The issue with BNCs in phase-critical radar timing systems is that the
delay through a BNC can jump by a few picoseconds from mechanical
rattling. If the signal traversing the BNC is subsequently multiplied
up into the GHz, the angular phase shifts can become intolerable.
Especially in a high-vibration environment.

BNCs are also somewhat leaky, even in the precision grades.

So, BNCs are usually forbidden except for test outputs. Only threaded
coax connectors, or mechanically stable blind-mate, or the like are
allowed.

Joe Gwinn

On Wednesday, 27 July 2022 at 21:37:14 UTC+1, Joe Gwinn wrote:
> On Fri, 22 Jul 2022 21:12:31 -0400, Phil Hobbs
> <pcdhSpamM...@electrooptical.net> wrote:
>
> >Joe Gwinn wrote:
> >> On Fri, 22 Jul 2022 21:38:39 -0000 (UTC), "Don" <g...@crcomp.net> wrote:
> >>
> >>> Joe Gwinn wrote:
> >>>
> >>> <snip>
> >>>
> >>>> Also, I'd lose the BNC connectors. Threaded connectors like SMA, TNC,
> >>>> and Type N are far better.
> >>>>
> >>>> Or use shielded twisted pair to carry the 1PPS pulses. This would
> >>>> work better over a backplane.
> >>>
> >>> This is good advice. Even though the lazy guy within me never truly
> >>> gives up his fight to take the easy way out with BNC.
> >>> Twisted pair (TP) sounds even easier than BNC. So, what's the
> >>> "catch" with TP? Where's the "gotcha" to make TP harder than BNC?
> >>
> >> Depends on what you are trying to do.
> >>
> >> For nanosecond edges, coax is pretty useful, but short range and often
> >> mechanically awkward.
> >>
> >> For microsecond edges at 1000 meters, RS422 over shielded twisted pair
> >> is pretty good.
> >>
> >> For bus length links, LVDS or the like.
> >>
> >> And so on. And there is always optical links.
> >>
> >> Joe Gwinn
> >>
> >
> >BNCs are the bomb, as long as you aren't putting 500 of them in series,
> >as with the old 10base2 coax Ethernet.
> >
> >TNCs are a very small niche, and N connectors belong only on spectrum
> >analyzers.
>
> The issue with BNCs in phase-critical radar timing systems is that the
> delay through a BNC can jump by a few picoseconds from mechanical
> rattling. If the signal traversing the BNC is subsequently multiplied
> up into the GHz, the angular phase shifts can become intolerable.
> Especially in a high-vibration environment.
>
> BNCs are also somewhat leaky, even in the precision grades.
>
> So, BNCs are usually forbidden except for test outputs. Only threaded
> coax connectors, or mechanically stable blind-mate, or the like are
> allowed.
>
N connectors have their problems too. I discovered that if they are hand-tightened
fairly gently they can introduce losses of 1 or 2 dB at about 1.2 or 1.3GHz.

John

Joe Gwinn wrote:
> On Fri, 22 Jul 2022 21:12:31 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> Joe Gwinn wrote:
>>> On Fri, 22 Jul 2022 21:38:39 -0000 (UTC), "Don" <g@crcomp.net> wrote:
>>>
>>>> Joe Gwinn wrote:
>>>>
>>>> <snip>
>>>>
>>>>> Also, I'd lose the BNC connectors. Threaded connectors like SMA, TNC,
>>>>> and Type N are far better.
>>>>>
>>>>> Or use shielded twisted pair to carry the 1PPS pulses. This would
>>>>> work better over a backplane.
>>>>
>>>> This is good advice. Even though the lazy guy within me never truly
>>>> gives up his fight to take the easy way out with BNC.
>>>> Twisted pair (TP) sounds even easier than BNC. So, what's the
>>>> "catch" with TP? Where's the "gotcha" to make TP harder than BNC?
>>>
>>> Depends on what you are trying to do.
>>>
>>> For nanosecond edges, coax is pretty useful, but short range and often
>>> mechanically awkward.
>>>
>>> For microsecond edges at 1000 meters, RS422 over shielded twisted pair
>>> is pretty good.
>>>
>>> For bus length links, LVDS or the like.
>>>
>>> And so on. And there is always optical links.
>>>
>>> Joe Gwinn
>>>
>>
>> BNCs are the bomb, as long as you aren't putting 500 of them in series,
>> as with the old 10base2 coax Ethernet.
>>
>> TNCs are a very small niche, and N connectors belong only on spectrum
>> analyzers.
>
> The issue with BNCs in phase-critical radar timing systems is that the
> delay through a BNC can jump by a few picoseconds from mechanical
> rattling. If the signal traversing the BNC is subsequently multiplied
> up into the GHz, the angular phase shifts can become intolerable.
> Especially in a high-vibration environment.
>
> BNCs are also somewhat leaky, even in the precision grades.
>
> So, BNCs are usually forbidden except for test outputs. Only threaded
> coax connectors, or mechanically stable blind-mate, or the like are
> allowed.
>
>
> Joe Gwinn
>

For synthetic-aperture radars, I believe that--small phase transients
are bad news. I had a similar experience long ago.

When I was a grad student, back around 1985-6, I built a heterodyne
interferometric scanning laser microscope.

It had a 13-bit phase digitizer, which used a nulling technique to
measure phase directly. There was an AM2504 successive-approximation
register, driving an AD DAC80 12-bit DAC, driving a homemade linearized
varactor phase shifter, with a MCL RPD-1 phase detector looking for a
null. (All dead-bug construction.)

One extra SAR cycle (with an external d-flop) made sure it was shooting
for the stable null, making 13 bits in all. It ran at the 60-MHz IF,
and pi phase was about 6000 LSBs, so 1 LSB was equivalent to

dt = 1/(6000 * 60 MHz) = 2.8 ps.

It had an associated calibrator, based on two 60-MHz crystal oscillators
locked together with a divide-by-360 counter on each. The counters had
(iirc) 11C90 10/11 prescalers, and one of them had the appropriate logic
for a pulse-swallower. That way the two outputs could be phase shifted
in exact 1-degree increments. A whole lot of attention was paid to
shielding and isolation amps and so forth, because any leakage of one
signal into the other above the -80 dB level would cause measurable
phase whoopdedoos.

Fortunately that was easy to verify by sitting on the pulse-swallowing
button, which moved the frequency enough to see any spurs on the
spectrum analyzer. (I borrowed an 8566A from another group for the
purpose.)

Calibrating the phase shifter with 1-degree steps made it easy to run a
cubic spline through the data to 1-LSB accuracy. Linearizing the phase
shifter meant that the conversion of 1 LSB to delta phase didn't vary
much across the range--it was always around 3 ps.

Jiggling coax cables during a measurement made for some very
entertaining image artifacts there too.

Cheers

Phil Hobbs

(Taking today off because it's so nice out, and because I can.)

--
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 Wed, 27 Jul 2022 14:18:34 -0700 (PDT), John Walliker
<jrwalliker@gmail.com> wrote:

>On Wednesday, 27 July 2022 at 21:37:14 UTC+1, Joe Gwinn wrote:
>> On Fri, 22 Jul 2022 21:12:31 -0400, Phil Hobbs
>> <pcdhSpamM...@electrooptical.net> wrote:
>>
>> >Joe Gwinn wrote:
>> >> On Fri, 22 Jul 2022 21:38:39 -0000 (UTC), "Don" <g...@crcomp.net> wrote:
>> >>
>> >>> Joe Gwinn wrote:
>> >>>
>> >>> <snip>
>> >>>
>> >>>> Also, I'd lose the BNC connectors. Threaded connectors like SMA, TNC,
>> >>>> and Type N are far better.
>> >>>>
>> >>>> Or use shielded twisted pair to carry the 1PPS pulses. This would
>> >>>> work better over a backplane.
>> >>>
>> >>> This is good advice. Even though the lazy guy within me never truly
>> >>> gives up his fight to take the easy way out with BNC.
>> >>> Twisted pair (TP) sounds even easier than BNC. So, what's the
>> >>> "catch" with TP? Where's the "gotcha" to make TP harder than BNC?
>> >>
>> >> Depends on what you are trying to do.
>> >>
>> >> For nanosecond edges, coax is pretty useful, but short range and often
>> >> mechanically awkward.
>> >>
>> >> For microsecond edges at 1000 meters, RS422 over shielded twisted pair
>> >> is pretty good.
>> >>
>> >> For bus length links, LVDS or the like.
>> >>
>> >> And so on. And there is always optical links.
>> >>
>> >> Joe Gwinn
>> >>
>> >
>> >BNCs are the bomb, as long as you aren't putting 500 of them in series,
>> >as with the old 10base2 coax Ethernet.
>> >
>> >TNCs are a very small niche, and N connectors belong only on spectrum
>> >analyzers.
>>
>> The issue with BNCs in phase-critical radar timing systems is that the
>> delay through a BNC can jump by a few picoseconds from mechanical
>> rattling. If the signal traversing the BNC is subsequently multiplied
>> up into the GHz, the angular phase shifts can become intolerable.
>> Especially in a high-vibration environment.
>>
>> BNCs are also somewhat leaky, even in the precision grades.
>>
>> So, BNCs are usually forbidden except for test outputs. Only threaded
>> coax connectors, or mechanically stable blind-mate, or the like are
>> allowed.
>>
>N connectors have their problems too. I discovered that if they are hand-tightened
>fairly gently they can introduce losses of 1 or 2 dB at about 1.2 or 1.3GHz.
>
Yes, all threaded connectors need to torqued to the "inspection
torque" value specified by the manufacturer, using a actual torque
wrench.

Joe Gwinn

On Wed, 27 Jul 2022 17:22:03 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>Joe Gwinn wrote:
>> On Fri, 22 Jul 2022 21:12:31 -0400, Phil Hobbs
>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>
>>> Joe Gwinn wrote:
>>>> On Fri, 22 Jul 2022 21:38:39 -0000 (UTC), "Don" <g@crcomp.net> wrote:
>>>>
>>>>> Joe Gwinn wrote:
>>>>>
>>>>> <snip>
>>>>>
>>>>>> Also, I'd lose the BNC connectors. Threaded connectors like SMA, TNC,
>>>>>> and Type N are far better.
>>>>>>
>>>>>> Or use shielded twisted pair to carry the 1PPS pulses. This would
>>>>>> work better over a backplane.
>>>>>
>>>>> This is good advice. Even though the lazy guy within me never truly
>>>>> gives up his fight to take the easy way out with BNC.
>>>>> Twisted pair (TP) sounds even easier than BNC. So, what's the
>>>>> "catch" with TP? Where's the "gotcha" to make TP harder than BNC?
>>>>
>>>> Depends on what you are trying to do.
>>>>
>>>> For nanosecond edges, coax is pretty useful, but short range and often
>>>> mechanically awkward.
>>>>
>>>> For microsecond edges at 1000 meters, RS422 over shielded twisted pair
>>>> is pretty good.
>>>>
>>>> For bus length links, LVDS or the like.
>>>>
>>>> And so on. And there is always optical links.
>>>>
>>>> Joe Gwinn
>>>>
>>>
>>> BNCs are the bomb, as long as you aren't putting 500 of them in series,
>>> as with the old 10base2 coax Ethernet.
>>>
>>> TNCs are a very small niche, and N connectors belong only on spectrum
>>> analyzers.
>>
>> The issue with BNCs in phase-critical radar timing systems is that the
>> delay through a BNC can jump by a few picoseconds from mechanical
>> rattling. If the signal traversing the BNC is subsequently multiplied
>> up into the GHz, the angular phase shifts can become intolerable.
>> Especially in a high-vibration environment.
>>
>> BNCs are also somewhat leaky, even in the precision grades.
>>
>> So, BNCs are usually forbidden except for test outputs. Only threaded
>> coax connectors, or mechanically stable blind-mate, or the like are
>> allowed.
>>
>>
>> Joe Gwinn
>>
>
>For synthetic-aperture radars, I believe that--small phase transients
>are bad news. I had a similar experience long ago.
>
>When I was a grad student, back around 1985-6, I built a heterodyne
>interferometric scanning laser microscope.
>
>It had a 13-bit phase digitizer, which used a nulling technique to
>measure phase directly. There was an AM2504 successive-approximation
>register, driving an AD DAC80 12-bit DAC, driving a homemade linearized
>varactor phase shifter, with a MCL RPD-1 phase detector looking for a
>null. (All dead-bug construction.)
>
>One extra SAR cycle (with an external d-flop) made sure it was shooting
>for the stable null, making 13 bits in all. It ran at the 60-MHz IF,
>and pi phase was about 6000 LSBs, so 1 LSB was equivalent to
>
>dt = 1/(6000 * 60 MHz) = 2.8 ps.
>
>It had an associated calibrator, based on two 60-MHz crystal oscillators
>locked together with a divide-by-360 counter on each. The counters had
>(iirc) 11C90 10/11 prescalers, and one of them had the appropriate logic
>for a pulse-swallower. That way the two outputs could be phase shifted
>in exact 1-degree increments. A whole lot of attention was paid to
>shielding and isolation amps and so forth, because any leakage of one
>signal into the other above the -80 dB level would cause measurable
>phase whoopdedoos.

Oh yes. Must use only double-shielded or better coax - RG-58 need not
apply.

Also must worry about power-frequency ground loops driving large
currents through the coax shield.

>Fortunately that was easy to verify by sitting on the pulse-swallowing
>button, which moved the frequency enough to see any spurs on the
>spectrum analyzer. (I borrowed an 8566A from another group for the
>purpose.)
>
>Calibrating the phase shifter with 1-degree steps made it easy to run a
>cubic spline through the data to 1-LSB accuracy. Linearizing the phase
>shifter meant that the conversion of 1 LSB to delta phase didn't vary
>much across the range--it was always around 3 ps.
>
>Jiggling coax cables during a measurement made for some very
>entertaining image artifacts there too.
>

Yes, exactly the same kinds of things bedevil phased-array radars.

Joe Gwinn

jlarkin@highlandsniptechnology.com wrote:
> On Tue, 26 Jul 2022 19:56:53 -0500, Les Cargill <lcargil99@gmail.com>
> wrote:
>
>> jlarkin@highlandsniptechnology.com wrote:
>>> On Fri, 22 Jul 2022 21:10:35 -0500, Les Cargill <lcargil99@gmail.com>
>>> wrote:
>>>
>>>> jlarkin@highlandsniptechnology.com wrote:
>>>>> On Thu, 21 Jul 2022 11:42:28 -0400, Phil Hobbs
>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>> <snip>
>>>>>> Phil Hobbs
>>>>>
>>>>> Mathematicians often like music. In my experience, music fandom is
>>>>> negatively correlated to engineering design skill. Different brain
>>>>> structure or something.
>>>>>
>>>>
>>>> Engineering is composition. Composition is the thin edge of the musical
>>>> wedge. Musicianship is different; it's pattern identification. As is
>>>> composition but in a different way. But it is all the same thing.
>>>>
>>>> It all depends on which wall you prefer to have your back against.
>>>
>>> I've always wondered about musicians. They have to play a piece
>>> hundreds of times to get it right.
>>
>> Some do; some don't. Session players from back when studio time
>> was the dominant cost probably played the parts on a song you later
>> heard on the radio on the first take.
>>
>>> Some have surely performed
>>> something thousands of times. Don't they get bored? Apparently not.
>>>
>>
>> There's too broad a spectrum to generalize. Some forms are better for
>> people with mild forms of OCD.
>>
>>> I design something, finish, and then want to design something entirely
>>> different.
>>>
>>> It depends on boredom thresholds.
>>>
>>
>> Much does.
>>
>>>>
>>>>> One other thing I see a lot is undue respect for standards. As in "you
>>>>> can't do that because it violates SCPI standards." Where are the SCPI
>>>>> Police when you need them?
>>>>
>>>> Over where they MATLAB.
>>>
>>> SCPI is send-and-forget. There is some query you can send to ask if
>>> the last command worked. And you can have an error queue that you can
>>> interrogate now and then for historical forensics.
>>>
>>> I told the customer that damn the specs, every command is going to
>>> reply with data, an error message, or "OK". They agree.
>>>
>>>
>>
>> And there you go turning a perfectly good full duplex channel into a
>> half duplex walkie-talkie channel :)
>>
>> It'll be fast enough.
>
> One might feel a little silly, having sent 14,000 commands to a box
> and then discovering that the power strip is off.
>

There are a small eternity of approaches. Line turnarounds are one.

--
Les Cargill

Don wrote:
> Les Cargill wrote:
>> jlarkin@highlandsniptechnology.com wrote:
>>> Les Cargill wrote:
>>>> jlarkin@highlandsniptechnology.com wrote:
>>>>> Phil Hobbs wrote:
>>>> <snip>
>>>>>> Phil Hobbs
>>>>>
>>>>> Mathematicians often like music. In my experience, music fandom is
>>>>> negatively correlated to engineering design skill. Different brain
>>>>> structure or something.
>>>>
>>>> Engineering is composition. Composition is the thin edge of the musical
>>>> wedge. Musicianship is different; it's pattern identification. As is
>>>> composition but in a different way. But it is all the same thing.
>>>>
>>>> It all depends on which wall you prefer to have your back against.
>>>
>>> I've always wondered about musicians. They have to play a piece
>>> hundreds of times to get it right.
>>
>> Some do; some don't. Session players from back when studio time
>> was the dominant cost probably played the parts on a song you later
>> heard on the radio on the first take.
>>
>>> Some have surely performed
>>> something thousands of times. Don't they get bored? Apparently not.
>>>
>>
>> There's too broad a spectrum to generalize. Some forms are better for
>> people with mild forms of OCD.
>>
>>> I design something, finish, and then want to design something entirely
>>> different.
>>>
>>> It depends on boredom thresholds.
>>>
>>
>> Much does.
>
> <snip>
>
> My much older, late partner used to play saxophone in High School in the
> 1950s. He belonged to an Illinois union and said you had to sight read
> sheet music to join the union.
> It was the big band era. To keep costs down, the band's core, of say
> six musicians, would tour and then hire local union musicians for a one
> night stand in order to fill out the big band.
>
> There's a Muscle Shoals studio interview somewhere out on the Inet. In
> it one of the sessions players talks about how he played by ear - at
> first. Until someone told him he needed to wise-up and learn how to
> sight read in order to earn the easiest money.
>
> My church's two volume songbook contains 634 songs. And a different mix
> is played each weekend. It's best to simply sight read the songs, as
> needed.
>
> Humble symphony orchestras work it about the same. Part-time musicians
> pick up their sheet music a day or two before a concert. There's simply
> not enough available time to "play a piece hundreds of times to get it
> right."
>

Just so. I think of solo concert pianists as the people who woodshed
the most. But they can probably produce a passable rendition on first
read.

> Danke,
>

--
Les Cargill

On 27/07/2022 15:13, Phil Hobbs wrote:
> Martin Brown wrote:

>> I expect they  are a lot better at it by now. In my day it involved
>> moving around furniture van loads of tweaked VHS video tape cassettes
>> from the big dishes to the correlator centres.
>
> As the wise man said, "Never underestimate the bandwidth of a truck full
> of tapes."

It works well and was very cost effective.
Tapes got reused after a while..
>
> Also, variously, a 747 full of tapes, CDs, DVDs, MicroSDs, etc.  A
> 747-load of 256-GB MicroSDs is about
> 256e12 B * 113,400 kg / 0.25 g = 1.16E+23 bytes.
>
> Six of them would be over 1 Avogadro.

The recent black hole images were using about 5e15 bytes of data each.

Disks and mass storage capacity generally have got a lot bigger. The
plastic chips in Star Trek (original) look huge in comparison to sD.

--
Regards,
Martin Brown