Frank, Try Polar Instruments web site. They have a downloadable demo for impedance calculations. The copy I am evaluating seems to work pretty good. Not sure of their address but a search should locate it for you. Franklin -----Original Message----- From: F. D. Bossert <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Date: 06 October, 1999 9:26 AM Subject: [TN] Impedance Calculation Sirs, Does anyone have a impedance formula for "Edge coupled surface microstrip"? Any help would be appriciated. Thanks ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################