🚀 go-pugleaf

On Wed, 11 Jan 2012 06:49:45 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

>On Jan 10, 9:48�pm, John Larkin
><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>> On Tue, 10 Jan 2012 18:27:01 -0800 (PST), George Herold
>>
>>
>>
>>
>>
>> <gher...@teachspin.com> wrote:
>> >On Jan 10, 12:09 pm, Phil Hobbs
>> ><pcdhSpamMeSensel...@electrooptical.net> wrote:
>> >> On 01/10/2012 01:47 AM, David L. Jones wrote:
>>
>> >> > Just thought some might be interested in hearing our recent guest on
>> >> > our Amp Hour radio show, Dr Howard Johnson of "Handbook of Black
>> >> > Magic" fame:
>> >> >http://www.theamphour.com/2012/01/10/the-amp-hour-77-winsome-waveform...
>>
>> >> > Lots of history of the book, signal integrity, Gigabit Ethernet
>> >> > development, 90 degree PCB bends, audiophoolery, and a whole bunch of
>> >> > other talk over almost 1 1/12 hours.
>>
>> >> > Dave.
>>
>> >> HJ has a mixture of good stuff and complete nonsense.
>>
>> >> I hope you grilled him a bit about his less sensible stuff, like that
>> >> hilariously erroneous video where he attempts to use electrostatics to
>> >> demonstrate that ground currents want to flow under traces. Of course,
>> >> the impedance levels are millions of times too high for inductance to be
>> >> a factor in that demo, but never mind. Have a look athttp://www.sigcon.com/Pubs/news/8_08.htmforthe whole ridiculous thing.
>>
>> >> (The current path is determined by corona discharge at the sharp corners
>> >> of the metal squares--if you look at all closely, you'll see that the
>> >> discharges always want to go out the corners of the squares.)
>>
>> >> Cheers
>>
>> >> Phil Hobbs
>>
>> >> --
>> >> Dr Philip C D Hobbs
>> >> Principal Consultant
>> >> ElectroOptical Innovations LLC
>> >> Optics, Electro-optics, Photonics, Analog Electronics
>>
>> >> 160 North State Road #203
>> >> Briarcliff Manor NY 10510
>> >> 845-480-2058
>>
>> >> hobbs at electrooptical dot nethttp://electrooptical.net
>>
>> >That is pretty silly.
>> >But certainly it's a good idea to keep a nice unbroken ground plane
>> >under the signal(s) that you really care about.
>>
>> >George H.
>>
>> That's often not practical. If the issue is a digital logic signal
>> cruising above a layer that has multiple power pours, with
>> design-rule-sized gaps between them, it's not likely to be a problem.
>> The power pours are big slabs of copper with a lot of capacitance to
>> the ground plane and to the universe, and are generally bypassed, so
>> as far as the signal trace is concerned, they may as well be over
>> ground.
>
>Sure, the power supply is as good as ground for all but the lowest
>frequencies.
>
>
>And a wavefront, even a 100 ps one, is not going to be much
>> disturbed by cruising over a narrow gap in the copper; it is filled
>> with epoxy. I've built test boards with this geometry, and with
>> deliberate slits in ground planes, and I've measured this stuff.
>
>Hmm, You've got tons more experience than me.  But there is an
>appealing logic to the slit idea... course I'm more than willing to
>abandon false ideas.
>
>>
>> One day I should lay out a horrible-example multilayer board and
>> document what really happens. I do often put test traces on production
>> boards, to see how we're doing on the impedance calculations.
>
>Yeah if you ever get some real data that would be wonderful.
>
>Muller's theorm #1.  If it happens, it must be possible.
>http://www.muller.lbl.gov/pages/Muller-theorems.htm
>
>>
>> http://johnlarkin.yolasite.com/pc-boards.php
>
>Yup, I was poking around your new website last night.

I'm just fooling around, getting a feel for it. I've got to figure out
how to organize sub-pages, or upgrade to the paid version that does
that stuff better.

And I need a section for political and economic rants.

John