[SI-LIST] Re: Floating Cable Shield

Craig, thanks for the book suggestion. Looks like a classic. I guess not 
that much has changed since 1976 (1st ed) or 1988 (2nd ed). I picked a 
used one up from Amazon, they are very inexpensive used. Ivor

on 10/11/2006 9:05 AM PDT Clewell, Craig wrote:
> Ivor, 
> 
> That is quite an interesting configuration, and it seems quite the waste of
> copper :>).  At the risk of becoming too loquacious I will direct you to
> Henry Ott's book "Noise Reduction Techniques in Electronic Systems".  There
> is a whole chapter dedicated to this question, and shows the good, the bad
> and the ugly ways of terminating a cable including what happens when you
> attach the shield at one end vs. both.
> 
> CC
> 
> -----Original Message-----
> From: Ivor Bowden [mailto:ivorlist@xxxxxxxxxxx]
> Sent: Wednesday, October 11, 2006 11:29 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Floating Cable Shield
> 
> 
> Hi,
> 
> I ran into what I thought was an interesting cable and am looking for 
> comments. This is an IDE cable on a new PC I got. The construction is 
> twisted pair ribbon cable (flat spots for IDCs between the twisted 
> sections), about 20" long, IDC both ends, a 3rd IDC about 7" from one 
> end. What makes the cable interesting to me is there are two braided 
> shields covering the bundled twisted pair sections, one about 8", the 
> other about 3.5". These shields have no connections, not to a drain 
> wire, not to each other and to to any circuit or frame ground, they are 
> entirely floating. My question is, how effective is this type of 
> "floating" shield, in terms of SI and EMI?
> 
> This also brings up the general question of cable shield termination, 
> circuit/chassis ground at both ends v.s. one end only v.s. floating; 
> what characteristics to expect in each case?
> 
> And that brings up the specific question of shield return treatment in 
> the connector area, single drain wire v.s. complete enclosure?
> 
> Thanks,
> 
> Ivor Bowden
> Hardware Engineer
> Curtiss-Wright Controls Embedded Computing
> Video and Graphics
> San Diego, CA 92121
> 
> 
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