John Larkin wrote:
> On Wed, 06 Jun 2012 20:09:05 -0800, Robert Baer
> <robertbaer@localnet.com> wrote:
>
>> John Larkin wrote:
>>> On Tue, 5 Jun 2012 07:48:12 -0700 (PDT), Bill Sloman
>>> <bill.sloman@ieee.org> wrote:
>>>
>>>> On Jun 5, 4:16 pm, John Larkin
>>>> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>>>> On Mon, 4 Jun 2012 23:09:42 -0700 (PDT),BillSloman
>>>>>
>>>>> <bill.slo...@ieee.org> wrote:
>>>>>> On Jun 4, 6:31 pm, John Larkin
>>>>>> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>>>>>> On Mon, 4 Jun 2012 08:51:29 -0700 (PDT),BillSloman
>>>>>
>>>>>>> <bill.slo...@ieee.org> wrote:
>>>>>>>> On Jun 4, 4:09 pm, John Larkin
>>>>>>>> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>>>>>>>> On Mon, 4 Jun 2012 00:34:20 -0700 (PDT),BillSloman
>>>>>
>>>>>>>>> <bill.slo...@ieee.org> wrote:
>>>>>>>>>> On Jun 4, 6:00 am, John Larkin
>>>>>>>>>> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>>>>>>>>>> On Sun, 3 Jun 2012 17:58:36 -0700 (PDT),BillSloman
>>>>>
>>>>>>>>>>> <bill.slo...@ieee.org> wrote:
>>>>>>>>>>>> On Jun 3, 10:09 pm, Phil Hobbs
>>>>>>>>>>>> <pcdhSpamMeSensel...@electrooptical.net> wrote:
>>>>>>>>>>>>> BillSlomanwrote:
>>>>>
>>>>>>>>>>>>>> On Jun 3, 9:02 pm, Fred Abse<excretatau...@invalid.invalid> wrote:
>>>>>>>>>>>>>>> On Sun, 03 Jun 2012 05:11:52 -0700,BillSlomanwrote:
>>>>>>>>>>>>>>>> We've just measured a coupling of 0.98 in a gapped RM14 core - EPCOS
>>>>>>>>>>>>>>>> gapped it down from 6000uH/root turn for an ungapped pair to 630nH per
>>>>>>>>>>>>>>>> root turn by grinding back the centre pillar by 0.4mm,
>>>>>
>>>>>>>>>>>>>>> I think that should be "per turn squared".
>>>>>
>>>>>>>>>>>>>> Wrong. Inductance is proportional to the square of the number of
>>>>>>>>>>>>>> turns, as long as they are closely coupled.
>>>>>
>>>>>>>>>>>>>> http://en.wikipedia.org/wiki/Inductor
>>>>>
>>>>>>>>>>>>> If L = alpha * N**2, then alpha has units of henries per turn squared.
>>>>>>>>>>>>> (Of course a turn isn't really a unit, just as a radian and a steradian
>>>>>>>>>>>>> aren't, but it sure isn't per square root turn.)
>>>>>
>>>>>>>>>>>> Applying dimensional analysis to a manufacturer's design fudge factor
>>>>>>>>>>>> is the sort of thing that physicists do.
>>>>>
>>>>>>>>>>> Engineers, too. My first engineering course at Tulane, first semister
>>>>>>>>>>> freshman year, was an introduction to units and dimensional analysis.
>>>>>>>>>>> It was taught by Dr Johnson, the Dean of the Engineering School, who
>>>>>>>>>>> thought it was important.
>>>>>
>>>>>>>>>>> Random noise increases as the square root of bandwidth, so we specify
>>>>>>>>>>> it as volts per root Hz.
>>>>>
>>>>>>>>>>> Inductance increases with turns squared, so we spec a core Al as
>>>>>>>>>>> henries per turn squared.
>>>>>
>>>>>>>>>>> See the difference?
>>>>>
>>>>>>>>>> It's 9:30am and my brain is working again, so yes - I do.
>>>>>
>>>>>>>>> Did you PWBC, post without benefit of coffee? I'm doing that now, and
>>>>>>>>> it's a great hazard.
>>>>>
>>>>>>>>>>>> It's not a particularly useful activity. Reminding junior engineers at
>>>>>>>>>>>> every possible opportunity that inductance is proportional to the
>>>>>>>>>>>> square of the number of turns in a winding is an extremely useful
>>>>>>>>>>>> activity, and saves loads of time at design reviews.
>>>>>
>>>>>>>>>>> They were probably polite enough to laugh at you after you left the
>>>>>>>>>>> room.
>>>>>
>>>>>>>>>> Perhaps. But they'd got the point - attention-getting devices don't
>>>>>>>>>> have to be pedantically correct to work. Look at Howard Johnson on
>>>>>>>>>> high speed signal propagation.
>>>>>
>>>>>>>>> He's as dangerous as Professor Moriarty.
>>>>>
>>>>>>>> I don't know about dangerous, but pedagogically horrible. If you
>>>>>>>> compare the lucid exposition of practical physics you get in Ralph
>>>>>>>> Morrison's "Grounding and Shielding Techniques in Instrumentation"
>>>>>
>>>>>>>> http://www.amazon.com/Grounding-Shielding-Techniques-Ralph-Morrison/d...
>>>>>
>>>>>>>> with the incoherent messes that Howard Johnson peddles,you go from the
>>>>>>>> sublime to the despicable.
>>>>>
>>>>>>> Yup. It's painful to read, even in the parts where he's technically
>>>>>>> correct.
>>>>>
>>>>>>>>> (Incidentally, the latest "Sherlock" was stunning.)
>>>>>
>>>>>>>> You mean the BBC televison series? We've been watching it here - we
>>>>>>>> get BBC 1 and 2 on the local cable - and liked it a lot.
>>>>>
>>>>>>> There are two running here now. The "classic" with Jeremy Brett,
>>>>>>> pretty good, and the modern-day one. It's the new one that I was
>>>>>>> referring to. I read all the Sherlocks several times when I was a kid,
>>>>>>> and revisit them now and then for a quick read.
>>>>>
>>>>>> That makes you a Holmesian, rather than a Sherlock fan. I've just re-
>>>>>> read Julina Barnes' "Arthur and George"
>>>>>
>>>>>> http://www.guardian.co.uk/books/2005/jun/26/fiction.shopping
>>>>>
>>>>>> which is essentially a portrait of Arthur Conan Doyle - a second rate
>>>>>> author, who didn't recognise Holmes as his greatest creation.
>>>>>
>>>>> He claimed to have written one story during a break in a cricket game,
>>>>> and killed him off because he was bored with him.
>>>>>
>>>>>> David Lodge does the English author biography a whole lot better.
>>>>>> "Author, Author" about Henry James, and "A Man of Parts" about
>>>>>> H.G.Wells, are both substantially better, perhaps because the subjects
>>>>>> had a bit more to offer.
>>>>>
>>>>> I can't read either of them, for some reason. HJ is especially boring
>>>>> to me...
>>>>
>>>> I can't read his novels - nothing ever happens. He wrote a few science-
>>>> fiction short stories in the sytle of H.G.Wells (who was a friend of
>>>> his) which aren't too bad.
>>>>
>>>> H.G.Wells was also a second rate novelist. His science fiction is
>>>> interesting - the ideas are sufficiently interesting to transcend his
>>>> defects as a novelist - if somewhat half-baked. His ideas about the
>>>> shape of things to come weren't all that accurate, but his expectation
>>>> that technological innovation would change the way we live was useful.
>>>>
>>>>> I've never made it halfway through any of his books. But I
>>>>> can, and do, reread the better Jane Austens and PG Wodehouses
>>>>> regularly.
>>>>
>>>> Jane Austen is well worth rereading. P G Wodehouse isn't - anything
>>>> that Wodehouse could do, Terry Pratchett can do better. Terry
>>>> Pratchett is a lot better educated than Wodehouse was, and it shows.
>>>>
>>>>> I'm now reading Enigma, the Turing biography. It's amazing the ideas
>>>>> that they had about computers in about 1950.
>>>>
>>>> Read old copies of Astounding Science Fiction - around 1950 - for
>>>> really bizarre ideas about computers.
>>>
>>>
>>> I have "IBM's Early Computers" and some stuff like that. The current
>>> concept of a base-2 synchronous-state-machine Von Neumann architecture
>>> seems so obvious now, but it sure wasn't in the early days. At least
>>> Turing appreciated that binary-decimal conversion could be done in
>>> software.
>>>
>>> Maybe we should have stuck with the Harvard architecture. Microsoft
>>> has never learned the difference between code and data.
>>>
>>> It would be interesting to consider what sort of computer could be
>>> built with early 1950s-sort of technology. Say, a few thousand dual
>>> triodes and core memory.
>>>
>>>
>> Check!
>> And there are ways to extend the life in the region of an order of
>> magnitude so that a tube hopper would not be sorely needed.
>
> Tube computers were reliable enough to be useful. One trick was to run
> midnight "margin tests" (run test code with varying filament and B+
> supplies) to weed out the weak tubes.
>
> But, having read up a bit on early computer architectures, it would
> just be interesting to design a computer with just dual triodes. The
> HP9100 programmable calculator only had about 20 flipflops, discrete
> transistor potted SIP things, and a CRT display. Early PDP8's used
> discrete logic board, like a flipflop or a gate, with transistors and
> diodes. Those sorts of architectures could have been done easily with
> tubes. What was lacking in the 1950s was the concepts.
>
>
Dual triode..makes me think of the classical 6SN7..tho for slightly
less space, 12AU7, 12AT7 or 12AX7 (any one or mix them as the mu is not
relevant with a decent FF design).
Or for even less space, a pair of nuvistors may do..