Gerry, I might have gotten the "values" mixed up. I think I intended to say the testing was requested to be done at 20us (micro) instead of the usual 200ps (picoseconds), not Db. Sorry for the confusion. I've been going around my office looking for the fabrication drawing this was specified on, but I can't find it. I hope I'm right this time. Best to talk with a fab house about impedance testing issues. Our fab house at that time couldn't test to the higher spped, so they had to have it done somewhere else. Also, ask for the certification on your fab drawing. They will supply it to you, if they DO do it. But, A great reference spec for impedance testing, unless you use the IPC-TM-650, is IPC-2141 (design for High Speed applications) Thanks for the input. Mitch >>> "Gerald G. Gagnon" <[log in to unmask]> 05/21/98 09:22am >>> Hello Mitch You wrote: Snip.... One thing we did was ask for impedance testing to be done to 200db levels instead of the standard 20db. This would show any and all discontinuities along the traces. Snip..... Question: With the impedance measurement techniques I've seen, this parameter is not mentioned. How does one determine from a given procedure, the dB level of the particular test they are running? BTW, I agree with your assertion that FR4 can be used with significant signal content in the 1Ghz range. Regards Gerry ################################################################ TechNet E-Mail Forum 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://jefry.ipc.org/forum.htm) for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum 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://jefry.ipc.org/forum.htm) for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################