In message <062220060528.732.449A2A99000B1179000002DC2200745672CECE020A900A02@comcas t.net>, dated Thu, 22 Jun 2006, neve...@comcast.net writes
>However, the issue is not the imbalance specification looking into the >DUT connector (test port, diff pairs....). The problem that I see here >is that CISPR22, 2005 is trying to emulate the imbalance of the >"Typical installation", and that I do not find any measurement data on >that, at least not for the CAT3-7 cabling. I do find the LCL (i.e. >balance) vs. frequency information in standards, but absolutely no >published data on LCL of "typical installations" to support them. So, I >don't know where these values in the standards are coming from. In a 'typical installation', the cable is connected to a port at each end. >Again, I am not talking here about imbalance at the DUT connector, but >imbalance that appears looking into the cabling from the DUT. When you do that, you see the combined effect of the cable impedances and the impedances of the port at the far end. So the LCL can be calculated from the specifications (if they exist) of those impedances or equivalent data. Maybe that is what was done in order to get the LCL figures specified in CISPR 22. > >The required level of imbalance for the ISN, combined with the max >possible (although not always used) amplitude of 10 BaseT (5.6 Vpk-pk) >makes me uncomfortable. On the other hand, if one uses the method with >current and voltage clamp, then there is no requirement for LCL, since >the measurement is done on the cable without any ISN. > >In my opinion, manufacturers of Class B products that use Ethernet, >e.g. laptops, PCs, SOHO routers/switches) should be concerned by the >still (in my opinion) not well defined requirements. -- 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
