In message <231db4b2f2634a4c94d87d89a4fa81d201542...@ny13ex011.global.ds.honeywell.c om>, dated Wed, 21 Jun 2006, "Sterner, David [S&FS]" <david.ster...@honeywell.com> writes
>If a pair of lines connects only two ports, each of the two ports is >100 ohms impedance, and the cable is uniform, please explain how the >Ethernet line can have an impedance imbalance between the two ports? I'm not sure what you mean by 'an impedance imbalance between the two ports'. We were not discussing impedance mismatch but mode conversion >from differential to common (leading potentially to emissions from the cable) or vice versa (leading to a lack of immunity). The functioning of balanced circuits in not radiating the signal and rejecting common-mode disturbances depends on the impedances at each end of the cable, from each conductor to a common reference point, being closely equal. Any voltage between the common reference points is then the input to a balanced bridge, and none of that voltage appears between the signal conductors. And vice versa, of course. While transformers CAN be made with excellent symmetry and very closely equal impedances to the common point, they are not always so designed, and it would be appropriate for the system standard to specify the permitted unbalance, in one of the many ways that can be done. I think this is what the original enquirer is asking about. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - 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 emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
