Michael The email I responded to (see below) stated that the example complete PCs radiated in excess of the EMC limits. The PC has cables, power supplies and other potential radiators besides the microstrip traces on the motherboard. **************************************************************************** ********* Nevertheless, ALL VENDOR PCs FAILED EMI WHEN THE CASES WERE OPEN---MISERABLY. The resonances I had predicted were confirmed to contain the worst offending frequencies. In the same time frame, I consulted to Motorola on their Power PC motherboards, with the exact same result---you had better have a good enclosure to pass FCC (or CISPR) Class B levels. Shipping PCs from Phoenix, AZ to Europe loosened marginally designed case sufficiently to cause EMI test failures in Europe that passed fine in the US. The cases were redesigned to increase seam contact ruggedness to resolve the problem. **************************************************************************** ********* Were the resonances predicted radiate directly or did the resonances conduct energy to other elements which radiated the energy? How did you determine the contribution from the microstrip vs. the other radiators in a complete PC? Tom Dagostino Teraspeed Consulting Group LLC Teraspeed Consulting Group LLC 2926 SE Yamhill St. Device Modeling Division Portland, OR 97214 13610 SW Harness Lane Beaverton, OR 97008 http://www.teraspeed.com 503-430-1065 tom@xxxxxxxxxxxxx -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of MikonCons@xxxxxxx Sent: Wednesday, October 22, 2003 4:10 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Traces don't cause EMI - really? In a message dated 10/22/2003 3:32:48 PM Pacific Standard Time, tom@xxxxxxxxxxxxx writes: In my experience, which I'm sure is not as broad as many who are contributing to this thread, is the cables were the big problem. Any noise on the ground, power or signals that were connected to the cables was radiated. This was much higher than anything on the board. ************ The above is a true statement for many (if not most) cases as radiated emissions increase with the square of frequency for common-mode radiation, but not for all EMI problems (either extenally detected or internally experienced....with resultng unacceptable performance). Loop circuits/antennas radiate only in proportion to frequency and are therefore not as big a problem at higher frequencies (where most of this discussion applies). As we all know, the generation of CM noise involves several other causes that have been discussed at length on this forum. Knowledge of ALL these phenomena (and their prevention) is what establishes the need for SI Engineers. Mike Michael L. Conn Owner/Principal Consultant Mikon Consulting *** Serving Your Needs with Technical Excellence *** ------------------------------------------------------------------ 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 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 ------------------------------------------------------------------ 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 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