4 ms·

The article is a nostalgic reminder of when I was first interested in electronics and got interested in quartz resonators for projects. Grinding down old war su

The article is a nostalgic reminder of when I was first interested in electronics and got interested in quartz resonators for projects. Grinding down old war surplus FT243-style crystals and other types so as to resonate at frequencies I needed was a common practice with hobbyists back then. I used many similar techniques to the same end of removing quartz which raised its frequency. Grinding materials included abrasives such as jeweler's rouge, cerium oxide, commercial polishes such as Brasso and Silvo and even HF solution. I'd place the quartz on a small section of plate glass and slide it through a slurry of the abrasive periodically testing its frequency until I'd reached my target. There's an art to this that's too long to mention here except to say abrasives were used strategically, course grinding would get me near the desired frequency and I'd finish off with a fine abrasive. Then there was the job of re-aging the crystal after its recent abuse to increase its stability. Other techniques were involved such as not lowering its Q factor, etc. which I'll not cover here. The most desired crystal cut was from the XT-plane (being the most stable) but it was generally difficult to get as it's only a small section of the quartz crystal (also each cut oscillates only over a limited range of frequencies). I used to have a book that explained these cuts in detail, their frequency ranges and electronic properties along with the basic crystallography which I lost years ago. A quick glance at the book would have shown that a great deal of science, engineering and skill is involved in the selection of quartz and its manufacture into useful resonators. BTW, the mentioning of HF will likely horrify chem-phobic readers. We were well aware of its dangers and took special precautions never to come in contact with it.

gilleain 8mo ago
> BTW, the mentioning of HF will likely horrify chem-phobic readers I would not say I am chem-phobic, but yes indeed that stood out. HF is nasty stuff, and yes requires some care I suspect. The other details are fascinating, though - the intersection of mechanical, crystallographic, and RF (?) properties of a crystal that you can adjust through abrasives and selection of the cut.
- adrian_b 8mo ago
  Working with HF was extremely difficult before WWII, but it has become much easier after the invention of Teflon. Teflon is not affected by HF, so if you use only vessels of Teflon to hold the HF solution and tweezers made of Teflon for handling anything that you submerge in the solution of HF, it works fine. Besides using Teflon for anything that is in contact with the HF solution, you must do all work under a hood that evacuates the vapors of HF emitted by the solution, otherwise handling a HF solution would be very dangerous. It is good that gaseous HF is lighter than air, so after being evacuated it will continue to rise in the air, while becoming more and more diluted.
  - hilbert42 8mo ago
    In my case the HF came in small black plastic cylindrical bottles of 50 perhaps 75 ml (could have been 100ml but that seems a bit big). Back then they were commonly available at local hardware stores. The bottle was flat on top from which protruded its 'neck' — more a threaded spigot of perhaps 8mm in dia. and about 10 to 12mm high with a small hole in it for the HF to exit. A red plastic cap screwed onto the thread to seal the bottle. If the bottle were ever knocked over (which it never was) very little would have spilled out (picture the threaded top and screw cap on the small bottles of Tabasco sauce and you've pretty much got it). So the HF only came out in drops which were poured directly into a small plastic beaker of about 50ml containing about 20ml of H2O and the crystal. The crystal rested on some finely corrugated plastic and not lying flat on the bottom to ensure the etching process was reasonably uniform. The operation was done outside and if I recall the HF was neutralised with NaOH. The soln was very dilute and the process could easily take over an hour and was used mainly to finish off crystals that had already been through the abrasive process. I don't know what type of plastic the bottle was made of but it was jet black.
vincnetas 8mo ago
So is this art of selecting right crystals is applicable for synthetic crystals also or these can be grown perfect each time to specifications?
- hilbert42 8mo ago
  I can't recall exactly but I'm pretty certain most crystal are synthetic these days, at least so for the common cuts. I'd imagine most watch quartz would be synthetic but that's only a guess.
jacquesm 8mo ago
That sinking feeling of knowing you've ground off just a bit too much...
- afandian 8mo ago
  I've just spent the weekend tuning brass reeds from an organ. It sounds like a very similar process, except you can grind both ends of the tongue to raise and lower frequency. And, if you're sneaky, you can add solder.
  - jacquesm 8mo ago
    Oh that is so cool. I played the one in Liepaja, Latvia for a bit and it was absolutely amazing. It's love/hate for me (like the harpsichord), I love the instruments but I usually do not like the music that is played on them because of the grating effect. I have pretty bad tinnitus which really spoils a lot of music for me, extremely annoying.
    - afandian 8mo ago
      Wow! I'm working on something much, _much_ smaller than that! https://blog.afandian.com/tags/harmonium/ https://blog.afandian.com/tags/harmonium/
      - jacquesm 8mo ago
        You are going to be leveling up in a whole bunch of skills.
        afandian 8mo ago
        Yes! Most important being calibrating what I should and shouldn't attempt yet.
        jacquesm 8mo ago
        I would just attempt it all and see where you get stuck. But one step at the time with total focus on that one step. I've done a lot of instrument repair over the years and the first one of a new class is always the hardest. So rather than to take the whole thing to pieces I'd fix just one aspect of it, reassemble and enjoy the improvement. Then fix the next thing. It's much more work than stripping the whole thing down but it keeps the gaps in your understanding small enough that you won't end up with a pile of parts rather than an instrument. I've been trying to remember the name of a particular instrument for you for the last 24 hours but so far no success, if I recall it I will post it here.
gtsnexp 8mo ago
This awesome. Could you perhaps remember the title of the book you lost?
- hilbert42 8mo ago
  I wish I could but it's s long while ago. More precisely the book wasn't lost but loaned to someone who never returned it and I lost track of him. The book was a harback with a bright yellow dust jacket and I think its title was printed in red. It was about 300 pages and was no lightweight, full of resonance equations, tables etc.—the sort of book you'd find in the lab of a commercial crystal manufacturer. Can't remember the price but it was damned expensive. At times over the years I've had need to refer to it and I still get a bit peeved when I think about it.
  - gtsnexp 8mo ago
    ok, could it be: Crystal Oscillator Design and Temperature Compensation :Marvin E. Frerking (1978). or perhaps Introduction to Quartz Crystal Unit Design : Virgil E. Bottom (1982)?
    - hilbert42 8mo ago
      Could well be either, it was around the late 70s early 80s when the book went walkabout. Damn nuisance my memory isn't better. However, I'd recognize it instantly if I saw it. Must check those references out. There may be enough info online for me to figure it out. Thanks.
      - gtsnexp 8mo ago
        Thank you!
        hilbert42 8mo ago
        "Crystal Oscillator Design and Temperature Compensation :Marvin E. Frerking (1978)." Ah, that has to be the book, just did a search and there's a photo of the cover on Amazon that I recognize. I said it was bright yellow with red writing and I was pretty close with its red lines and bits. 240 pages and not 300, but that's not too bad after close on 50 years. And I was correct about the price too, it is expensive, Amazon has it at $110 for the hardback. Good one!
hilbert42 8mo ago
Heavens, that should be AT cut not XT. What on earth was I thinking of? Some of you guys should have picked that up. ;-)
- hilbert42 8mo ago
  Further to my unforgivable boo-boo. This article provides a pretty good introduction to the subject and there's a diagram of a quartz crystal at the beginning indicating the position of AT cuts in relation to the crystal and other cuts. I've seen much more detailed diagrams of the crystal and cuts/cutting angles but I can't find one online. . Those precision diagrams are required by those who cut the quartz at the start of the manufacturing process. https://xoprof.com/2023/09/unleashing-the-mystery-of-crystal-cuts/ https://xoprof.com/2023/09/unleashing-the-mystery-of-crystal...

gilleain 8mo ago

> BTW, the mentioning of HF will likely horrify chem-phobic readers I would not say I am chem-phobic, but yes indeed that stood out. HF is nasty stuff, and yes requires some care I suspect. The other details are fascinating, though - the intersection of mechanical, crystallographic, and RF (?) properties of a crystal that you can adjust through abrasives and selection of the cut.

adrian_b 8mo ago
Working with HF was extremely difficult before WWII, but it has become much easier after the invention of Teflon. Teflon is not affected by HF, so if you use only vessels of Teflon to hold the HF solution and tweezers made of Teflon for handling anything that you submerge in the solution of HF, it works fine. Besides using Teflon for anything that is in contact with the HF solution, you must do all work under a hood that evacuates the vapors of HF emitted by the solution, otherwise handling a HF solution would be very dangerous. It is good that gaseous HF is lighter than air, so after being evacuated it will continue to rise in the air, while becoming more and more diluted.
- hilbert42 8mo ago
  In my case the HF came in small black plastic cylindrical bottles of 50 perhaps 75 ml (could have been 100ml but that seems a bit big). Back then they were commonly available at local hardware stores. The bottle was flat on top from which protruded its 'neck' — more a threaded spigot of perhaps 8mm in dia. and about 10 to 12mm high with a small hole in it for the HF to exit. A red plastic cap screwed onto the thread to seal the bottle. If the bottle were ever knocked over (which it never was) very little would have spilled out (picture the threaded top and screw cap on the small bottles of Tabasco sauce and you've pretty much got it). So the HF only came out in drops which were poured directly into a small plastic beaker of about 50ml containing about 20ml of H2O and the crystal. The crystal rested on some finely corrugated plastic and not lying flat on the bottom to ensure the etching process was reasonably uniform. The operation was done outside and if I recall the HF was neutralised with NaOH. The soln was very dilute and the process could easily take over an hour and was used mainly to finish off crystals that had already been through the abrasive process. I don't know what type of plastic the bottle was made of but it was jet black.

vincnetas 8mo ago

So is this art of selecting right crystals is applicable for synthetic crystals also or these can be grown perfect each time to specifications?

hilbert42 8mo ago
I can't recall exactly but I'm pretty certain most crystal are synthetic these days, at least so for the common cuts. I'd imagine most watch quartz would be synthetic but that's only a guess.

jacquesm 8mo ago

That sinking feeling of knowing you've ground off just a bit too much...

afandian 8mo ago
I've just spent the weekend tuning brass reeds from an organ. It sounds like a very similar process, except you can grind both ends of the tongue to raise and lower frequency. And, if you're sneaky, you can add solder.
- jacquesm 8mo ago
  Oh that is so cool. I played the one in Liepaja, Latvia for a bit and it was absolutely amazing. It's love/hate for me (like the harpsichord), I love the instruments but I usually do not like the music that is played on them because of the grating effect. I have pretty bad tinnitus which really spoils a lot of music for me, extremely annoying.
  - afandian 8mo ago
    Wow! I'm working on something much, _much_ smaller than that! https://blog.afandian.com/tags/harmonium/ https://blog.afandian.com/tags/harmonium/
    - jacquesm 8mo ago
      You are going to be leveling up in a whole bunch of skills.
      - afandian 8mo ago
        Yes! Most important being calibrating what I should and shouldn't attempt yet.
        jacquesm 8mo ago
        I would just attempt it all and see where you get stuck. But one step at the time with total focus on that one step. I've done a lot of instrument repair over the years and the first one of a new class is always the hardest. So rather than to take the whole thing to pieces I'd fix just one aspect of it, reassemble and enjoy the improvement. Then fix the next thing. It's much more work than stripping the whole thing down but it keeps the gaps in your understanding small enough that you won't end up with a pile of parts rather than an instrument. I've been trying to remember the name of a particular instrument for you for the last 24 hours but so far no success, if I recall it I will post it here.

gtsnexp 8mo ago

This awesome. Could you perhaps remember the title of the book you lost?

hilbert42 8mo ago
I wish I could but it's s long while ago. More precisely the book wasn't lost but loaned to someone who never returned it and I lost track of him. The book was a harback with a bright yellow dust jacket and I think its title was printed in red. It was about 300 pages and was no lightweight, full of resonance equations, tables etc.—the sort of book you'd find in the lab of a commercial crystal manufacturer. Can't remember the price but it was damned expensive. At times over the years I've had need to refer to it and I still get a bit peeved when I think about it.
- gtsnexp 8mo ago
  ok, could it be: Crystal Oscillator Design and Temperature Compensation :Marvin E. Frerking (1978). or perhaps Introduction to Quartz Crystal Unit Design : Virgil E. Bottom (1982)?
  - hilbert42 8mo ago
    Could well be either, it was around the late 70s early 80s when the book went walkabout. Damn nuisance my memory isn't better. However, I'd recognize it instantly if I saw it. Must check those references out. There may be enough info online for me to figure it out. Thanks.
    - gtsnexp 8mo ago
      Thank you!
      - hilbert42 8mo ago
        "Crystal Oscillator Design and Temperature Compensation :Marvin E. Frerking (1978)." Ah, that has to be the book, just did a search and there's a photo of the cover on Amazon that I recognize. I said it was bright yellow with red writing and I was pretty close with its red lines and bits. 240 pages and not 300, but that's not too bad after close on 50 years. And I was correct about the price too, it is expensive, Amazon has it at $110 for the hardback. Good one!

hilbert42 8mo ago

Heavens, that should be AT cut not XT. What on earth was I thinking of? Some of you guys should have picked that up. ;-)

hilbert42 8mo ago
Further to my unforgivable boo-boo. This article provides a pretty good introduction to the subject and there's a diagram of a quartz crystal at the beginning indicating the position of AT cuts in relation to the crystal and other cuts. I've seen much more detailed diagrams of the crystal and cuts/cutting angles but I can't find one online. . Those precision diagrams are required by those who cut the quartz at the start of the manufacturing process. https://xoprof.com/2023/09/unleashing-the-mystery-of-crystal-cuts/ https://xoprof.com/2023/09/unleashing-the-mystery-of-crystal...