> >Ray; > >Since the effective dielectric constant is a function of the reference >ground plane distance and the trace width, ground plane distance does >effect velocity. > >Justin >Intel , Sacramento > Justin- Effective dielectric constant is a weak but complex function of stack-up geometry for microstrip lines where the fields around the line are partly in the air and partly in the substrate material, however for stripline geometries where the substrate material is both above and below the signal conductor I don't believe there is that dependency. -Ray Sun Microsystems Menlo Park, CA ------------------------------------------------------------------ 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