Interesting things, crystals.
I used to work in a telephone equipment factory. We made our own crystals and
crystal filters. The first step of grinding the blanks...
.... There was this giant kettle looking thing. Maybe 4 feet in diameter. It was filled
with an abrasive slurry. At the top was a rotating plate and over that another plate filled
with crystal-sized holes. They would load the blanks in and the whole thing would turn like a
merry go round, getting the crystals rough tuned.
As the crystals were ground, they would emit RF. Because they were...well.. crystals.
People monitored the rough frequency with a Hallicrafters short wave radio clipped to the kettle.
A final adjustment was performed with the Dual Chamber Frequency plater. It had two chambers,
and production workers would load chamber 1 while it was plating in chamber 2. Frequency was monitored
with an HP vector volt meter. At resonance, the phase would swing through zero, and the system would
stop plating, and the chamber would open, and the other one would close.
As an instrument shop tech, I did a bit of work on both of these systems - troubleshooting the Hallicrafters for the rough step, and the vector voltmeter on the plater. The vector voltmeter had
four HP hot carrier diodes in its probe. Those matched sets of four were mondo expensive, and I saved
us some money by matching diodes with an HPIB-controlled voltmeter, controlled by a program that I
wrote on an HP9825 desktop computer.
Ah, youth.
- Jerry, KF6VB
