Dear Technetters, Many designers and PCB fabricators ask me why differential traces often measure higher impedances than predicted. The following new application note explains how the physical characteristics of woven glass reinforced substrates cause this to happen. And, how you can help minimize the differences between your calculations and the finished board. http://www.polarinstruments.com/support/cits/AP139.html I am sure you will find this note helps explain some of the underlying reasons why sometimes the measured values of impedance vary from the theoretical. Hope this is of interest Kind regards Martyn Gaudion www.polarinstruments.com --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------