Alan This would be no different than a floating metalic enclosure around any piece of electronic equipment. You have parasitic capacitance everywhere, and, in the case of a cable with such a metal jacket, the coupling is quite high. Thus, everything is coupled to everything else. In addition, you have yourself a very nice floating dipole antenna, which will radiate all of that coupled energy very efficiently. Essentially, the manufacturer has created a capacitively coupled antenna system.
regards, Scott Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com Teraspeed® is the registered service mark of Teraspeed Consulting Group LLC Hudson, Alan wrote: >G'Day! > >Came across an oddity today which has failed to stimulate any memories (from >about the time the old King died!) of basic electromagnetic theory. A >well-known computer Company supplies what it calls "shielded ribbon cables". >When we examine one of these we find it's essentially a metallic braid >sleeve around a standard ribbon cable. The braid isn't connected to anything >(not even a drain wire at the connector ends). > >So what level of shielding is this going to give - if any? > >I could imagine signal lines being capacitively coupled to the braid and >then capacitively coupled to any 0V lines in the ribbon. But I can also >imagine signal lines being capacitively coupled to other signal lines. >Similarly with external signals hitting the braid - they could go to either >the signal or 0V lines - yes/no? > >I know I should know the answer to this, but obviously, today at least, if I >had a brain I'd be dangerous! > >:-) > >Regards, > >Alan > > - 2005 IEEE Symposium on Product Safety Engineering 3-4 October Schaumburg, IL http://www.ieee-pses.org/symposium This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
