More Hardcore Homebrew — Cutting Quartz Crystals
Yesterday’s linked article about negative resistance oscillators got me thinking about the possibility of creating a radio where literally every component was made by hand. Okay, I’m not quite ready to make my own wire, but the zinc oxide oscillator that Nyle Steiner seemed like it was only one step away from reaching a reasonable approximation to that goal: instead of a transistor, it used an oxidized strip of zinc. Making potentiometers and capacitors isn’t that hard: the book Voice of the Crystal will give you some ideas about those.
The one element that seems like a specialized, manufactured bit of kit is the quartz crystal. But I suspected that even this could be manufactured, I just didn’t know where to look for information. But then I rembered that my ARRL membership included access to historical back issues of the QST magazine archive, going back to the time of World War I. Sure enough, a short search later uncovered a pair of articles from 1935 by Ivan Loucks, W9ON. Sadly, I can’t reproduce links to the articles here (they are copyrighted), but the first is from the Jan, 1935 QST, and is entitled Cutting Quartz Crystal Plates and the second from February is entitled Grinding and Finishing Quartz Crystal Plates. Combined, the two articles give a pretty good description of how quartz crystals can be cut from raw quartz, dimensioned and then ground and polished into crystals suitable for making oscillators.
This information opens up the possibility that you could make a radio transmitter with no premade components. I think that’s pretty interesting.
Addendum: Here is a history of the development of quartz crystal technology. It pointed me at an additional pair of articles about crystal control by J. Herbert Hollister from 1928 and 1930 in QST. From the article Quartz Crystal Facts, Hollister opens with this:
With just a year of the narrowband era behind us, we find the ranks of the quartz crystal exponents growing daily. At this time last year most of us thought crystal control was only some trick arrangement for the other fellow to play with and squander his money on. There were few, however, who did not envy the crystal controlled station with the beautiful bell-like note which was always to be found at exactly the same point on the dial.