[time-nuts] Glass Envelope Quartz Crystals

[Tim Shoppa]

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 at 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.
>
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