Maybe HP5071s will get their ADEV when optical clocks will officially rule...
On Fri, Mar 26, 2021 at 9:40 AM Magnus Danielson <[email protected]> wrote: > > Hi, > > On 2021-03-25 19:21, Poul-Henning Kamp wrote: > > -------- > > Attila Kinali writes: > > > >> Does someone of those who own a 5071 have long-term ADEV data? > >> I'm looking for multi-year data. While there are plenty of ADEV > >> plots online, most of them stop at 1Ms or even at 100ks. > > As I understand it, cesium beams are considered "primary" standards > > because once the ADEV hits the floor, it stays down there ? > > "primary" standard means different things in different context. > > In telecom, it means it adheres to ITU-T G.811 specifications, which > effectively puts within 1E-11 in maximum frequency error, which is what > analog cesiums can deliver. Most of the cesiums we attain as hobbyists > was designed to meet this spec. The underlying specification driving it > was to keep data-slip rate between two operators down to once in 70 > days. It was reasonably achieveable with the technology at hand and for > the total cost so I think it was fair. > > In metrology "primary standard" has a complete different meaning, and in > practice all clocks we hobbyists gets to have would not fit, they would > all be more or less good "secondary standards". > > The sales people for vendors will be happy to underblow the > understanding of you being able to buy and have your own "primary > standard". If it where, you would not be needing traceability to > anything else, but you end up needing to have that anyway, and in > reality the "primary" reference is actually one of the few that > contributes to the international realization. I've seen a few of those, > but not in my basement. > > The "primary reference" is not about ADEV hitting the floor, all devices > do that (for a strict definition of what should be measured in ADEV). > It's about the context one consider it "primary". > > It would be cool to say one has a "primary standard", and depending on > context I have several working or none. Coolness aside, when talking to > metrology folks and national metrology labs, I might have some clocks, > but I do not call them "primary reference", because most of them does > not have that either. > > So, I think we should be careful with the term, it's get thrown around > too lightly. > > Cheers, > Magnus > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send an > email to [email protected] > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
