[time-nuts] Glass Envelope Quartz Crystals

[Bob Camp]

Hi

You can indeed pick up the 32 KHz output of the crystal with a microphone.
We used to do that and used the result to drive a counter. The information
was used to manually (yes it once was done that way) set the watch modules
on frequency. 

Depending on the size and design of the crystal, the Q can be anywhere up
to about 150K on a 32 KHz crystal. Some designs struggle to get to 50K.

Bob

> On Feb 7, 2016, at 7:31 AM, Tim Shoppa <tshoppa at gmail.com> wrote:
> 
> 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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