🚀 go-pugleaf

On Thu, 25 Jun 2009 13:33:59 -0700, the renowned John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>On Thu, 25 Jun 2009 22:22:29 +0200, Fred Bartoli <" "> wrote:
>
>>Joerg a �crit :
>>> Fred Bartoli wrote:
>>>> John Larkin a �crit :
>>>>> On Thu, 25 Jun 2009 16:31:09 +0800, TonyS <scarborofun@gmail.nspm.com>
>>>>> wrote:
>>>>>
>>>>>> John Larkin wrote:
>>>>>>> On Wed, 24 Jun 2009 21:42:07 -0700, <castlebravo242@att.net> wrote:
>>>>>>>
>>>>>>>> "David L. Jones" <altzone@gmail.com> wrote in message 
>>>>>>>> news:h8B0m.53620$FI5.3564@newsfe12.iad...
>>>>>>>>> Check out a rather unusual phenomenon you can see on your 
>>>>>>>>> oscilloscope in my latest blog (#14):
>>>>>>>>> http://www.alternatezone.com/eevblog/
>>>>>>>>> See if you can get it to happen on your scope!
>>>>>>>>> I'll offer a free subscription to my blog for the best screen 
>>>>>>>>> shot posted :->
>>>>>>>>>
>>>>>>>>> Oh, and the probe doesn't have to be shorted either.
>>>>>>>>>
>>>>>>>>> Have fun.
>>>>>>>>> Dave.
>>>>>>>>> -- 
>>>>>>>>> ================================================
>>>>>>>>> Check out my Electronics Engineering Video Blog & Podcast:
>>>>>>>>> http://www.alternatezone.com/eevblog/
>>>>>>>>>
>>>>>>>>>
>>>>>>>> When I worked a Century Data we had a problem with our new reel to 
>>>>>>>> reel vaccuum column tape drive when ever someone would walk by the 
>>>>>>>> drive when it was reading it would get data errors. The problem 
>>>>>>>> was that the shield on the cable from the heads to the preamp was 
>>>>>>>> grounded on both ends.
>>>>>>>>
>>>>>>>> Bob
>>>>>>> That's usually the best way to ground shields.
>>>>>>>
>>>>>>> John
>>>>>>>
>>>>>>>
>>>>>> IIRC head signals mostly went via twisted pair. If they had a shield 
>>>>>> as well we would certainly not ground them on both sides.
>>>>>>
>>>>>
>>>>> You *want* large amounts of high-frequency common-mode noise?
>>>>>
>>>>
>>>> Probably. Lots of people don't understand this and I've seen this kind 
>>>> of mistake (opened shield) recommended in lots of highly regarded EMC 
>>>> books.
>>>>
>>>> But that's really nice for us. (Joerg?)
>>>>
>>> 
>>> Yeah! But shhht, don't spill the beans here, at least not until I am 
>>> retired :-))
>>> 
>>
>>I think I'll retired after you, but this kind of misconception is 
>>sufficiently widely spread that we don't have to worry :-)
>
>Yup. Once people get fixated on "ground loops" they are forever lost
>to reason.
>
>Ditto high-speed "return currents."
>
>John

Two coaxial shields with one end of each grounded at opposite ends is
pretty nice. 



Best regards, 
Spehro Pefhany
-- 
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