Indeed yor estimation is correct. The Q-factor of the tiny tuning-fork crystals @32.768 kHz is typically between 20,000 and 50,000. The dynam al capacitance is a couple of fF, and thus R1 is between 10k to 80k depending on the sizeRgdsBernd  DK1AG Von meinem Samsung Galaxy Smartphone gesendet.-------- Ursprüngliche Nachricht --------Von: Tim Shoppa <tshoppa@gmail.com> Datum: 07.02.2016 13:31 (GMT+01:00) An: Discussion of precise time and frequency measurement <time-nuts@febo.com> Betreff: Re: [time-nuts] Glass Envelope Quartz Crystals I know that the tiny modern 32kc/32.768kc tuning fork crystals continue to produce output for a second or so after power is shut off. This leads to my guess that typical modern tuning fork crystals have a Q of 30,000 or so. I'm not sure any manufacturer actually publishes Q for their tiny tuning fork crystals but maybe from ESR and other crystal motional parameters I could come up with some other way to derive Q from a modern tuning fork datasheet? I wonder if I had a ultrasonic microphone if I could audibly pick up a modern tiny tuning fork crystal. (My ears have never been good to 32kc even when I was younger!) I remember when I was younger, I liked listening to the high pitched hum of my dad's tuning fork Accutron (360Hz). Tim N3QE On Sat, Feb 6, 2016 at 11:17 PM, Morris Odell <vilgotch@bigpond.net.au> wrote: > This is a very interesting discussion. I have experimented with some audio > frequency crystals in the 3-6 kHz range. I don't know what they came out of > but it was probably some sort of FDM telephony or telegraphy equipment. > They're in the form of vacuum mounted bars with 4 plated terminals in tall > 7 pin or octal tube envelopes. When suitably driven they oscillate audibly > like a bell ringing and as a result of the very high Q they even keep > ringing for a few seconds after the power is turned off. Unfortunately I > don't have access to a stroboscope. I'd like to do something useful with > them on display, perhaps a clock for people with presbyacusis who wouldn't > notice the sound :-) > > Morris > > >> You have it right, iovane. At the least, they should be protected > >> from light, > >> thermal radiation, and emf.   Won'drous things will happen if the > >> crystal and > >> its structure are subjected to radiation through the glass. I'd > >> suggest a foam gator wrap in a tin can as a minimum. Put the > >> oscillator cat in there too. > > > >   I have a 100 kHz glass "Crystal Unit" made by G.E.C., type JCF/193 > > with a serial number and sealed in a valve/tube with seven pins. > > I removed it from my Eddystone EA12 that I bought from Tom Roberts, > > G3YTO, SK 1985. It has a black shield with a spring inside at the top > > so that it grips the base. The valve that produced 100 kHz markers for > > dial calibration failed and I don't use the EA12 these days. > > It will be interesting to see how stable it is and what the effect of > > light and heat on it is when I start experimenting. > > _______________________________________________ > 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.