Very interesting Ken. Perhaps a CISPR subcommittee should revisit the standardized methods of measurement, particularly with regard to conducted emissions above approx 10MHz _____________________________________________________________________________________
Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Compliance Engineer From: Ken Javor <ken.ja...@emccompliance.com> To: EMC-PSTC@LISTSERV.IEEE.ORG List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: 04/08/2010 07:50 PM Subject: Re: [PSES] 50 ohm LISN (AMN) ________________________________ The important effect of the length of power cables between test sample and LISN is not decoupling, but vswr. Once the cable approaches a quarter wavelength, the test sample doesn’t see the LISN anymore; it sees the impedance of the cable as a mismatched transmission line. That is the reason for the 10 MHz cut-off for conducted emissions in MIL-STD-461 CE102. At least in MIL-STD-461, the tolerance on LISN impedance is 20%, and that should suffice to cover serial number to serial number variations in impedance. Ken Javor Phone: (256) 650-5261
