Bob He stated 0.01Hz EFC tuning range was adequate. Gave no spec as to how close to nominal frequency is required though.
Bruce > On 16 March 2017 at 10:53 Bob Camp <kb...@n1k.org> wrote: > > > Hi > > By most modern definitions, “high stability” starts around 1x10^-12 (1 ppt) > at a tau of 1 second to > 10 seconds. There are $20 eBay OCXO’s that run at that level. With a > fundamental crystal you > aren’t going to get to that point. > > How much EFC range are you after? > > How good a CNC setup do you have? > > What kind of temperature test setup do you have? > > Simply put, the design approach is a “test over temperature / collect data -> > optimize” loop. > Without good frequency vs temperature data, you are flying totally blind. > Even on a production > design, this is how it’s done. The parts you fiddle are likely to be odd > shaped chunks of metal > that fit here or there. > > Bob > > > On Mar 15, 2017, at 3:36 PM, Gilles Clement <clemg...@club-internet.fr> > > wrote: > > > > Hi, > > I have a bunch of 5.184Mhz crystals. Large metallic tanks: HC33U case > > Maybe not OCXO grade, but I build a simple oscillator with a 4060 chip > > placed in a double oven, and reached 10E-9 short term stability up to 10sec > > tau. > > Not bad, so wondering if I can get better with a more advanced design. > > Gilles. > > > > > >> Le 15 mars 2017 à 12:45, Bob Camp <kb...@n1k.org> a écrit : > >> > >> Hi > >> > >> Where do you plan on getting an OCXO grade crystal at an odd frequency > >> like > >> that? Much of the performance of a good OCXO is in the crystal. Doing a > >> proper > >> design on one is a lot of work. You *might* think that having a design for > >> 5.000000 > >> MHz would give you a good design for 5.000050 MHz. I have empirical > >> evidence that > >> this isn’t the case. Many years later, I’m still utterly amazed that this > >> is the way things > >> work in the crystal business ….( = it’s not just a design issue, it’s also > >> a business decision) > >> > >> More or less the crystal needs to be: > >> > >> 1) Cut specifically to have a turn at a temperature that makes sense for > >> your application. > >> 2) A “large blank” design (for it’s frequency) > >> 3) In a cold weld package (most of the normal crystals are resistance weld) > >> 4) Run through a high vacuum / high temperature process > >> 5) Be plated with gold rather than something like silver or aluminum > >> (unless it’s at VHF). > >> 6) Have a motional capacitance that makes sense for your EFC range ( > >> normally = minimize) > >> 7) Preferably be an SC or modified SC cut. > >> > >> This is for a high stability part. The list does keep going on for a > >> while, but that should > >> give you a pretty good idea. > >> > >> Bob > >> > >>> On Mar 15, 2017, at 3:11 AM, Gilles Clement <clemg...@club-internet.fr> > >>> wrote: > >>> > >>> Hi, > >>> So what is the « best » design for DIY a high stability OCVXO ? > >>> I am looking after one, needed for an exotic frequency : 5184kHZ > >>> Thx, > >>> Gilles. > >>> > >>> > >>>> Le 14 mars 2017 à 18:02, Richard (Rick) Karlquist > >>>> <rich...@karlquist.com> a écrit : > >>>> > >>>> > >>>> > >>>> On 3/14/2017 4:03 AM, Bruce Griffiths wrote: > >>>> > >>>>> > >>>>> Looking at oscillator circuits like the HP10811A will give some idea of > >>>>> some of the additional complexity required for a overtone operation. > >>>>> Dissecting a few ocxos may also be helpful. Some start with a 10MHz > >>>>> crystal and a Colpitts sustaining stage and use a 74HC74 or similar to > >>>>> divide the 10Mhz by 2 and drive the output pin. Even when a sinewave > >>>>> output is required often a CMOS inverter drives the output pin via an > >>>>> LC filter. > >>>>> > >>>>> Bruce > >>>>> > >>>> > >>>> I don't agree here. The 10811 is not a good tutorial for general > >>>> oscillator design. Because it is SC cut, it has a complicated > >>>> mode suppression network across the base emitter junction to > >>>> suppress mode B as well as the fundamental. > >>>> > >>>> The E1983A oscillator uses the same crystal (in a low profile > >>>> package). You can read my paper about it and see that I > >>>> used a very simple bridged tee oscillator circuit. That is > >>>> all you need to select the right overtone and mode. > >>>> > >>>> This is the same circuit that I used at Zeta Labs 40 years > >>>> ago to design hundreds of custom VCXO's, up to the 9th > >>>> overtone. It simply worked every time, unlike various other > >>>> designs that were in use at Zeta. > >>>> > >>>> Around 1985, I got a consulting gig at Equatorial Communications > >>>> to redesign their 5th overtone VCXO. Only about half of the > >>>> crystals would work in their circuit. They had thousands > >>>> of "reject" crystals. I just used my old Zeta circuit and > >>>> all the crystals started working again. > >>>> > >>>> Equatorial owned the 10 meter dish that you used to see on > >>>> your right going south on 237 just before passing over > >>>> Central Expressway in Mountain View. > >>>> > >>>> Rick N6RK > >>>> > >>>> > >>>> _______________________________________________ > >>>> 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.
