So does anyone actually think that a radio manufacturer took 100 radios off the shelf and tested them simultaneous to calculate out some average and derive at the number they state? I highly doubt that many radios were tested especially considering the cost of some of these radios!!!
On Sat, Aug 26, 2017 at 2:03 PM, Forrest Christian (List Account) < [email protected]> wrote: > Need to correct my example: > > 10 devices fail in the first year. 10% per year. 50% would be at 5 > years. So the MTBF is 5 years. Adam's explanation is likely also > accurate. > > On Sat, Aug 26, 2017 at 12:01 PM, Forrest Christian (List Account) < > [email protected]> wrote: > >> My understanding is that MTBF is usually calculated by taking a certain >> sample size, then seeing how many fail over a certain amount of time. >> From this number you can then use statistics to determine how many years >> the rest will last. >> >> A simplified example would be if you take 100 devices, and 10 fail in the >> first year, then you assume that 5 would fail per year, and the mtbf would >> be 5 years. >> >> Remember 'M' is mean. Or average. Which roughly means that only half >> of the units will still be working in that amount of time. It doesn't mean >> your particular radio will last that long, just that half of the radios >> will last that long. Yours might fail in 10 days or a year or never.... >> >> Personally, I believe that this method is rather dubious since some >> electronic parts exhibit wear-out. Electrolytic capacitors as an example. >> Even if very few devices fail at 5 years, there is a good chance that >> most will fail at 20 years after the electrolytic caps have dried out. >> >> On Sat, Aug 26, 2017 at 9:29 AM, Kurt Fankhauser < >> [email protected]> wrote: >> >>> Where do these MTBF ratings come from by radio manufacturers? Are they >>> just made up numbers the manufacturer "hopes" that the product can achieve >>> or is actual testing done to get to these numbers? I thought i seen a radio >>> once with a 90 year MTBF rating. How they hell can they determine that? The >>> components in the radio didn't even exist 90 years ago. >>> >>> If a radio manufacture states in the spec sheets that the radio has a 40 >>> year MTBF rating but then also admits that after 4 years expect to have >>> problems due to a design flaw, what does that mean? Is the expected MTBF >>> rating only good in a "lab environment" under "ideal conditions"? >>> >>> Seems to me the MTBF is just marketing fluff and actually doesn't mean >>> crap.... >>> >> >> >> >> -- >> *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* >> Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 >> [email protected] | http://www.packetflux.com >> <http://www.linkedin.com/in/fwchristian> >> <http://facebook.com/packetflux> <http://twitter.com/@packetflux> >> >> > > > -- > *Forrest Christian* *CEO**, PacketFlux Technologies, Inc.* > Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 > [email protected] | http://www.packetflux.com > <http://www.linkedin.com/in/fwchristian> <http://facebook.com/packetflux> > <http://twitter.com/@packetflux> > >
