Thanks Jackson, I think I have seen that lately, I thought that was a GPS problem related to the transition between holdover and locked but I was unable to reproduce it with a GPS simulator. It is really pronounced on the C-Mac in the unit.
Thomas Knox > CC: time-nuts@febo.com > From: saidj...@aol.com > Date: Sun, 3 Nov 2013 09:33:57 -0800 > To: time-nuts@febo.com > Subject: Re: [time-nuts] The 5MHz Sweet Spot > > Bob, et. al., > > Lots of opinions in this discussion, but none of it discusses the elephant in > the room affecting todays' vendors: > > Random crystal instability versus manufacturing techniques. > > I can buy oscillators from multiple vendors that have -115dBc at 1Hz or > better and noise floors of -182dBc. That technology is well understood and > has been mature for a very long time and to me its boring. Recently Ulrich > Rhode even had a great article in the Microwave Journal detailing how exactly > to build one of those units. > > But what does it help me to have -115dBc if the darn thing jumps 50ppt every > two to three days?? > > Crystal jumps are the biggest menace facing users of crystals/oscillators > today and so far I have never been given a reasonable explanation from any of > the vendors out there what causes it and how to avoid it or how they plan to > address it. > > In fact no vendor we know tests for it to levels of sub-ppt over days which > is what is necessary for any disciplined application as disciplining will > clearly show even the smallest crystal jumps. Almost every vendor will do a > frequency test only, where a phase test would be needed. > > Users of crystals/oscillators are left with doing an exhaustive yield test > during burn-in to find bad crystals. We test our boards for 3 days and more > to weed out jumpy crystals, and its a pain and very expensive to have to do > this on finished goods as rework is in order for units that fail. > > The results are staggering, some vendors consistently have jumpy product, > others consistently have excellent product, all have at least occasional > batches that are worse to far worse than standard deviation. Some are so bad > that one batch may yield 95% and the next batch of the same exact product > will only yield 50% or less! > > I think this is the area of Quartz processing that has the least amount of > research invested into it, and as anyone that has seen their Z38xx unit jump > up and down in phase can attest to its a menace and can ruin one's day. I > wish there were something besides yield testing that can be done to avoid > manufacturing and shipping bad crystals to integrators. BVA seems to be one > of those solutions, but how many BVA's have we seen in products that cost > $400 retail?? > > Bye, > Said > > On Nov 3, 2013, at 5:09, Bob Camp <li...@rtty.us> wrote: > > > Hi > > > > Rubiola is looking at resonators he can buy off the shelf. They are > > constrained by the commonly available packages. The Q x F product does not > > suddenly stop going up at 5 MHz. There is good documentation that it keeps > > on going as the frequency goes down. Is Q everything - of course not. > > However *if* you wanted a much higher Q crystal than the 5 MHz, it could be > > built if you had the time and the money. > > > > Bob > > > > On Nov 3, 2013, at 7:58 AM, gandal...@aol.com wrote: > > > >> Hi Bob > >> > >> I've seen this topic discussed here before and it does seem to raise some > >> quite strong emotions and there does seem to be some confusion. > >> > >> I can remember quite clearly, historically at least, 5MHz being commonly > >> promoted as the optimum frequency for crystal oscillators on the basis > >> that > >> 5MHz crystals had this "sweet spot", presumably when it came to > >> temperature > >> stability. > >> An online search today hasn't been very forthcoming and unfortunately > >> most > >> of my reference library remains in storage, so I can't provide instant > >> references, but I know I've also seen this in print and can still > >> envisage the > >> graphs used to demonstrate it. > >> > >> The nearest to a current reference I've found is this comment from Enrico > >> Rubiola on page 156 of "Phase Noise and Frequency Stability in > >> Oscillators"......... > >> "The process described relies on the ability to estimate the resonator's > >> quality factor. Experience indicates that the product voQ is a technical > >> constant for piezoelectric quartz resonators, in the range from 1 x 10^11 > >> to 2 > >> x 10^13. As a matter of fact, the highest values are found in 5MHz > >> resonators. ............." > >> > >> I have no axe to grind on this, aside from willingly admitting to being > >> one of the confused:-), but if this is a misconception is it possible to > >> address why such a situation might have arisen? > >> > >> Regards > >> > >> Nigel > >> GM8PZR > >> > >> > >> > >> In a message dated 03/11/2013 01:46:01 GMT Standard Time, li...@rtty.us > >> writes: > >> > >> Hi > >> > >> I believe that you are talking to two very different groups, one who > >> actually design the crystals and the other who use the products that are > >> designed. One is talking about what they can buy, the other is talking > >> about what > >> could / could not be done and why. > >> > >> Bob > >> > >> On Nov 2, 2013, at 8:22 PM, Tom Knox <act...@hotmail.com> wrote: > >> > >>> From reading your past posts I must respect your opinion. Your are > >> obviously extremely educated on the subject. So why is there some > >> disagreement > >> in two very knowledgeable groups? > >>> > >>> Thomas Knox > >>> > >>> > >>> > >>>> From: li...@rtty.us > >>>> Date: Sat, 2 Nov 2013 18:44:18 -0400 > >>>> To: time-nuts@febo.com > >>>> Subject: Re: [time-nuts] The 5MHz Sweet Spot > >>>> > >>>> Hi > >>>> > >>>> The only thing that the 5 MHz 3rd crystal is “optimum” for is a holder > >> that will accept a 0.55” max diameter blank. > >>>> > >>>> Bpb > >>>> > >>>> On Nov 2, 2013, at 6:06 PM, Tom Knox <act...@hotmail.com> wrote: > >>>> > >>>>> Mike I think we must be talking to the same smart people. I think 5MHz > >> was adopted over 3MHz simply because 5MHz multiplies to other commonly > >> used frequencies with greater ease. I think the top frequency standards > >> have > >> evolved to 5MHz Third Overtone SC cut crystals for a reason. The > >> evolution > >> has gone on from the days of Tesla and improved greatly during the glory > >> days of Quartz in the years leading up to atomic standards with countless > >> hours of experimentation and research. Those lessons learned are > >> constantly > >> examined through the lens of the latest science. I may be wrong, but I > >> have > >> not heard of any extreme design prototype quartz oscillator with superior > >> Phase Noise and Stability. Our house standard F1 a cesium fountain is > >> used > >> roughly one month every few months to characterize roughly 12 5071A > >> cesium > >> standards steering about 5 MHM 2010 cleaned up with a number of 8607 > >> option > >> 08 oscillator. (The equipment choices are not a recommendation or > >> endorsement, and there are po > >>>>> ssibly m > >>>>> any product that could meet or exceed the performance of these fine > >> products.) But the oscillators selected are 5MHz third Overtone SC cut. > >>>>> > >>>>> Thomas Knox > >>>>> > >>>>> > >>>>> > >>>>>> From: mfe...@eozinc.com > >>>>>> To: n1...@alum.dartmouth.org; time-nuts@febo.com > >>>>>> Date: Sat, 2 Nov 2013 09:50:50 -0400 > >>>>>> Subject: Re: [time-nuts] The 5MHz Sweet Spot > >>>>>> > >>>>>> Exactly - I mentioned this on here about 3 years ago and all of the > >>>>>> self-proclaimed geniuses poo-pooded it. I was told early in my > >> engineering > >>>>>> career in the early 70's, by a very smart man, when I thought I had > >> all of > >>>>>> the answers, that considering all of the trade-offs regarding > >> performance, > >>>>>> around 3 MHz for a crystal is best, operating in the 3rd overtone > >> mode, > >>>>>> hence the slow progression from the 1 and 5 MHz standards to 10 MHz. > >> Now, > >>>>>> getting close to 70, I just see what I can learn from all the "smart" > >> people > >>>>>> on here, and keep quiet most of the time. Regards - Mike > >>>>>> > >>>>>> Mike B. Feher, EOZ Inc. > >>>>>> 89 Arnold Blvd. > >>>>>> Howell, NJ, 07731 > >>>>>> 732-886-5960 office > >>>>>> 908-902-3831 cell > >>>>>> > >>>>>> -----Original Message----- > >>>>>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] > >> On > >>>>>> Behalf Of David McGaw > >>>>>> Sent: Saturday, November 02, 2013 1:30 AM > >>>>>> To: Discussion of precise time and frequency measurement > >>>>>> Subject: Re: [time-nuts] The 5MHz Sweet Spot > >>>>>> > >>>>>> This all seems to be forgetting that the crystals are usually > >> operated at > >>>>>> 3rd or 5th harmonic. The crystal in a 10811A is 10 MHz/3rd overtone. > >> A > >>>>>> high quality 5 MHz/5th overtone crystal is really a 1 MHz > >> fundamental, a > >>>>>> large piece of quartz. Running at a harmonic greatly reduces the > >> influence > >>>>>> of the package. > >>>>>> > >>>>>> David > >>>>>> > >>>>>> > >>>>>> _______________________________________________ > >>>>>> 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. > >>>> > >>>> _______________________________________________ > >>>> 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. > >> > >> _______________________________________________ > >> 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. > > > > _______________________________________________ > > 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. _______________________________________________ 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.
