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 <kb8tq@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 <clemgill@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 <kb8tq@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 <clemgill@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 <richard@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.

Hi Ok, I missed that. Unless there is also a trimmer cap, the EFC will be >> 0.01Hz if it needs to be on frequency for any rational amount of time. If the crystals are the typical old fundamentals, they may age 5 to 10 ppm / year when heated to OCXO temperatures. That’s +/- 25 to +/- 50 Hz just for the first year. Bob > On Mar 15, 2017, at 6:11 PM, Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > > 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 <kb8tq@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 <clemgill@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 <kb8tq@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 <clemgill@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 <richard@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.