🚀 go-pugleaf

On Jan 12, 4:30 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Thu, 12 Jan 2012 02:11:46 -0800 (PST),BillSloman
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> <bill.slo...@ieee.org> wrote:
> >On Jan 12, 3:13 am, John Larkin
> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >> On Wed, 11 Jan 2012 16:49:18 -0800 (PST),BillSloman
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> >> <bill.slo...@ieee.org> wrote:
> >> >On Jan 11, 8:22 pm, Phil Hobbs
> >> ><pcdhSpamMeSensel...@electrooptical.net> wrote:
> >> >> On 01/11/2012 01:43 PM, John Larkin wrote:
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> >> >> > On Tue, 10 Jan 2012 18:02:50 -0800 (PST),BillSloman
> >> >> > <bill.slo...@gmail.com> wrote:
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> >> >> >> On Jan 10, 4:55 pm, John Devereux<j...@devereux.me.uk> wrote:
> >> >> >>> Robert Macy<robert.a.m...@gmail.com> writes:
> >> >> >>>> On Jan 10, 2:28 am,BillSloman<bill.slo...@ieee.org> wrote:
> >> >> >>>>> On Jan 10, 7:47 am, "David L. Jones"<altz...@gmail.com> wrote:

<snip>

> >> >> >> Motorola's ECL applications notes on board layout were rather useful,
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> >> >> > Just don't trust their microstrip equation!
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> >> >They looked okay in the range 50R to 75R.
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> >> Yup. And they give silly, even negative, impedances for traces outside
> >> a narrow width zone.
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> >Which is more or less what I went on to say in the next paragraph -
> >you seem to suffer from premature ejeculation.
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> You suffer from nostalgia for the times, decades ago, when you
> actually did things... most of which didn't work.

I do feel a certain amount of nostalgia for the times when I did
things - which all actually worked when management didn't cancel the
projects before we'd got to actual hardware. Management did frequently
decide that they couldn't sell the stuff that I was allowed to get
working.

All of this is entirely irrelevant to the observation that you went
off at half-cock, busily saying pretty much what I'd already posted,
but you couldn't find a way of justifying that, so you posted one more
of your inaccurate insults instead.

> >> >Specialised textbooks give
> >> >longer and more complicated expressions that give rather different
> >> >results for microstrips and strip-line with higher and lower
> >> >characteristic impedances.

<snip>

> >At current ECLinPS speeds everything gets averaged over a few
> >millimetres of track. The extra capacitance implicit in a right-angle
> >bend on a 5OR track might be perceptible, but you can pretty much
> >eliminate it by chamfering the corner, or making two 45-degree bends
> >in quick succession.
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> That's what the ancient Moto book said. It was stupid at 10K speeds
> and it remains stupid at EclipsPlus speeds. I can barely discern a
> right angle with a zoomed-up 30 ps TDR edge. The weave of the
> fiberglass changes the impedance more than a sharp corner. Vias are
> hugely more important than right angles.

Obviously.

I'm a bit surprised that you are bothering to do time domain
reflectometry on FR-4 boards. Rogers make a bunch of substrates that
work rather better at very high frequencies. A Cambridge Instruments
we made the outer layers of six layer boards for the GaAs parts with
isocyanate-resin-bounded Teflon cloth. The inner layers (that weren't
exposed to the GaAs signals) were regular FR-4 which kept the board as
a whole rigid - they were triple extended Eurocards and we didn't want
them flopping around.

Our printed circuit board supplier charged us extravagantly for the
boards - he had to buy a lot more of the isocyanate-resin-bonded
Teflon cloth substrate than he need to make up our first batch of
boards, and he knew we were pushing the state of the art, and - very
wisely - wasn't prepared to wait for us to order a production batch of
boards to cover the expenditure.

--
Bill Sloman, Nijmegen