On Wed, 31 Mar 2021 16:44:40 +0000 "Poul-Henning Kamp" <p...@phk.freebsd.dk> wrote:
> It used to be that 5MHz was the "hot spot" for crystals on the > parameters we care about as time-nuts. Depends on what kind of time-nut you are ;-) If you are going for high frequencies beyond 1GHz, then a mesa type high frequency BAW is the best you can do (given you don't want to use frequency comb to divide down a cryogenic silicon cavity). As Bob wrote, for low-frequency, high stability applications, the lower the frequency of the crystal the better. Or rather, the thicker the crystal the better. I.e. you want to use an as low frequency crystal with an as high as possible overtone. Unfortunately, to make full use of the properties of low frequency crystals, you need to scale the diameter with the frequency. Otherwise, the energy loss due to the edges of the crytal will limit the Q. For historical reasons, 3rd overtone 5MHz turned out to be the lowest that could be done economically with the avaible tools and methods and still fit the size constraints. Today we could probaly go lower, but the market demands for large crystal units is shrinking steadily and, as Bob wrote a few times in the past, nobody has the tooling to do so. Attila Kinali -- The driving force behind research is the question: "Why?" There are things we don't understand and things we always wonder about. And that's why we do research. -- Kobayashi Makoto _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.