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

>> I expect they&nbsp; 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.&nbsp; 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

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

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

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

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

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 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

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 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.&#4294967295; 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&#4294967295; 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.