[time-nuts] Glass Envelope Quartz Crystals

Bob Camp kb8tq at n1k.org
Sun Feb 7 08:12:14 EST 2016


They are wonderful works of industrial art. Unfortunately, except for the strobe trick, there is not 
a lot of use you can get out of them. A modern 32 KHz watch crystal is a much more accurate 
thing to use for a clock or watch. About the only exception to that broad sweeping generalization 
would be the GT cut 100 KHz plates (they are roughly square). You would need to find them in
a vacuum enclosure. That was rarely done due to their > 1” on a side sort of dimensions. They
might or might not beat the 32 KHz crystal on long term stability. They would beat it in terms of
temperature stability. 

As you probably have guessed, the gear this sort of thing went into was pretty large. “row after
row of racks” is how it often is described when implemented in a “central hub” setting. The pick
off points down the line would not have been that crazy. 


> On 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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