I recently picked up a rack of old gear from the garage of a local silent key. They were in rough shape with leaky caps, rust, and corrosion, but deep inside a crystal oven I found this.
This was part of an FAA frequency standard. It was mounted in an aluminum enclosure with about 1/4″ walls. This was surrounded by about a half inch of styrofoam and then a slightly thinner aluminum enclosure. That outer enclosure had three resistors on each side used to heat it and that was enclosed (with some air space) in a wooden box.
To align this, there was a WWV receiver and various other gear. I’d only be guessing on the accuracy, but I recently ordered a GPSDO (GPS disciplined oscillator) that is better than 1 part-per-billion in accuracy. I don’t doubt that is significantly better than this could offer even when it was freshly calibrated.
There is a slight chip in the upper right hand corner of the quartz bar. It is held in place by what looks like fishing line and a series of springs.the leads aren’t visible–they are whisker thin and soldered to the gold plating on the bottom of the quartz bar.
I was going to build a 100 kHz marker generator with this and still might on day, but for now I’ll probably stick with the 10 MHz GPSDO around the home lab.
“With a soldering iron in one hand, a schematic in the other, and a puzzled look on his face.”