Hi Well, if you make OCXO’s that way, you will not be in business for very long. At least not selling to the major OEM’s ( or to any customer who actually checks the parts).
Bob > On Apr 11, 2020, at 10:26 AM, David C. Partridge > <[email protected]> wrote: > > Well, that's how it's supposed to be done, but these days the usual (and > often only) criterion other than part value (e.g. 15V 200uF +/- 10%) seems to > be cost (cheapest == best). > > Sad isn't it. > > David > -----Original Message----- > From: time-nuts [mailto:[email protected]] On Behalf Of Bob > kb8tq > Sent: 11 April 2020 14:05 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] OCXO and fluctuations after EFC adjustment > > Hi > > Bottom line is that, as long as one is careful about *which* vendors supply > which > parts, normal parts do the job. Nobody is going to publish that selection > process > or the results. They very much want the “other guy” to have to do it on their > own. > > The 78L12 might look just like one from 5 other vendors. It also might work > 10X > better than the others. Those caps may look pretty normal. They came from > “this guy” and not “those guys”. That cheap looking thermistor might have > spent > a few years in evaluation before it was approved for use. > > There is a lot of work that goes into component selection. It simply does not > result in $20 bulk metal film parts with 0.2 ppm/ C specs getting used. It is > a > lot more difficult to spot in the finished product. > > Bob > > > > > >> On Apr 11, 2020, at 3:15 AM, John Moran, Scawby Design >> <[email protected]> wrote: >> >> On Fri, 10 April 2020 14:31:53 -0700 Rick wrote: >> >> >>> At this time, I will give my usual speech about IMHO the fact that >> >>> since the invention of the DDS on a chip, EFC should no longer be used >> >>> for high performance oscillators. >> >> During my 50 years in the electronics industry I have always been puzzled >> about one aspect of crystal oscillators. They go to great lengths to use a >> precise piece of quartz as the heart, because of its unique properties, and >> then add standard external components - capacitors, varactors, Zeners, etc. >> to tweak its frequency. All these components vary far more than the original >> piece of quartz ... hence my confusion. >> >> I know it is practically impossible to grind a crystal to exactly the >> frequency you want, and it then drifts over time, but what is the logic of >> using relatively wildly varying components to adjust the quartz? Are their >> temperature and ageing characteristics swamped by the superior crystal? >> >> In all the papers I have ever read, the subject is never mentioned ... you >> just add a variable capacitor and/or an EFC circuit and job done. >> >> I guess this is showing my total ignorance here, but I would like to know. >> >> Maybe this is at the heart of Rick's usual speech? >> >> John >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
