Hi Andy, I'm going through something like that right now. My intent was to do it all by myself. This is at a system level. Individual assemblies such as communication modules and power supply modules I have calculated using the Bellcore TR-332 Reliability Standard 5th Edition that addresses MTBFs and FITs (Failure In Time). 1 FIT = 1 failure / Billion Hours MTBF = (10^9)/FITs For simple assemblies: It's all spelled out in TR-332 for *assemblies*. I've done it with an Excel spreadsheet that I copied right out of the standard. I also bought special software from a company called Relex that does an excellent job. Bellcore also sells software for the same thing, but as of 2 years ago, my experience with it was less than favorable. Perhaps they have improved it. TR-332 even provides tables of industry accepted FITs for all sorts of parts. For systems with redundancy: But, this doesn't cover what happens at a system level. Trying to calculate this by hand, one must use reliability probablistic models where the math can get rather hairy. I tried doing this, but the downfall is that my system has redundancy. Just simply running the numbers from some given equations doesn't take into acount things such as "mission time", "availability", and most important repair. If I ran just dry numbers for my system, I am assuming that the system gets locked away in a closet and stays there until everything fails without regard to someone ever coming by and replacing failed units. For simple assembly calculations, get a copy of Bellcore TR-332 (I think it's about $150) Tel: 201-829-4785 For system level calculations, request a more accurate MTBF calculation by contacting two labs: John Healey at Bellcore (the man responsible for TR-332) Tel: 732-758-3065 Dr. Ronald Giuntini at Wylie Labs (extremely helpful person) Tel: 205-837-4411 Regards, Doug > From: Andy Kowalewski <[log in to unmask]> > > Hi, > > The company I'm currently working with has been asked to provide an > unusual form of MTBF figure across a complex microwave/baseband system. > > Can anyone point us to a source of information we can use to build the > figure? ################################################################ 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 the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################