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.