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 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu |**************************************************************************| This email is intended only for the person or entity to which it is addressed and may contain confidential, proprietary and/or privileged material. Any review, distribution, reliance on, or other use of this information by persons or entities other than the intended recipient is prohibited. If you receive this message in error, please immediately notify the sender and delete it and all copies of it from your system. Thank you. |**************************************************************************| ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu