In a message dated 10/22/2003 2:43:36 PM Pacific Standard Time, alexh1@xxxxxxxxxxxxx writes: I routinely see requirements for low cost office equipment that the case be non-metalized plastic. And this is with SDRAM memory interfaces running at 100+ Mhz. It's not necessarily easy, and it may be impossible for a multi-vendor, multi card, multi cable environment like a PC. If one is designing a card for a PC, he/she may not be as attentive to EMI issues knowing it will operate in a metal enclosure. ******** Your "multi-vendor, multi-card" comment is right on target. I have redesigned plastic-encased, fully self-contained units to pass FCC Class B by building the Faraday "enclosure" right on the outer layers of the PCB. However, the common plug-in cards of normal PCs depend on using a shielded enclosure around the entire assembly and generally have not been designed for stand-alone compliance. My military product design experience strongly supports designing daughter cards that are inherently shielded to avoid coupling between adjacent cards. Of course, military requirements are more demanding relative to consumer applicatiions. NOTE: The loop antenna formed by a single-ended trace over a ground plane radiates normal to the PCB. Likewise, the single-ended traces on an adjacent card RECEIVE best (and are therefore most susceptible) for normally impinging fields. The result is that microstrip-based designs DO radiate sufficiently to cause EMI problems on adjacent microstrip-based cards. That's another reason I recommend stripline for ALL fast-edge signal traces. These days, that criteria covers most signals. 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