Hi The thing that amazed me was that there were at least two of us in the room who *knew* the answer, and neither of them worked for HP ....
Bob On Apr 23, 2010, at 2:16 AM, Magnus Danielson wrote: > Hi Bob, > > On 04/23/2010 04:10 AM, Bob Camp wrote: >> Hi >> >> Back in the late 70's HP was pushing their ADEV test setup to us. They >> hauled one in (yes indeed >> more than one box) for a demo. It took them most of the morning to get it in >> from the parking lot >> and set up / warmed up / running. > > To much amusement I am sure. > >> They ran us through a little presentation on how ADEV has two slopes (I >> *wish* I'd kept a copy...). >> We brought out some sample oscillators, and ran them through. *Surprise* >> more than two slopes. >> I then asked them "what do the other slopes mean?". No answer .... we'll get >> back to you .... >> mumble mumble .... They never did get back to me. > > Depending on the oscillator you expect to see white, 1/f and 1/f^3 phase > modulation noise or white, 1/f^2 and 1/f^3 phase modulation noise. Looking at > tabulated Allan variance: > > http://en.wikipedia.org/wiki/Allan_variance#Power-law_noise > (see also Tom's PDF) > > We see that white and 1/f is weakly different such that they can be expected > easilly be mistaken for having the same slope. The 1/f^3 noise has a flat > Allan variance response. So, their oscillator during testing may simply have > been of one kind and the oscillator you brought out of the other. > > The Allan variance unability to separeate the white and 1/f noise triggered > the development of the modified Allan variance, but that only happend after > that incident. > >> Needless to say they would have been a lot more likely to make the sale if >> they had one of your >> one page charts. > > A copy of Leesons paper (a two-page thing) in 1966 would have helped a lot. > > Cheers, > Magnus > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
