[HN Gopher] Quartz crystals
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Quartz crystals
Author : gtsnexp
Score : 125 points
Date : 2026-02-08 08:26 UTC (1 days ago)
(HTM) web link (www.pa3fwm.nl)
(TXT) w3m dump (www.pa3fwm.nl)
| intrasight wrote:
| Nice. I'm an EE by education. We weren't taught how such a key
| piece of the puzzle worked.
| zeofig wrote:
| The account of the youtube video linked in the article has been
| terminated apparently. Anyone know why or if there's an alternate
| link?
| maxbond wrote:
| https://web.archive.org/web/20160422054642/https://www.youtu...
| Simboo wrote:
| Now that was nice. I liked that a lot thank you for sharing.
| speakspokespok wrote:
| With a crystal of the right dimensions and correct input voltage
| could one feel the crystal vibrating?
| Isamu wrote:
| You mean could you get it down to a low enough frequency? Hmm I
| guess you can get down into audio frequency but maybe the
| amplitude will be tiny, you probably want a piezo mechanism
| that will give you more of a rumble.
| kurthr wrote:
| As mentioned in the article there are a lot of common watch
| crystals that oscillate at 32.768 kHz, but they are tuning
| fork crystals rather than bulk mode (or modern SAW), which
| have much higher frequencies. It would be challenging to
| lower the frequency of these, but perhaps you could evaporate
| Au or W onto the tips and reseal them to get into the audible
| frequencies. Much easier would be to get two crystals which
| beat against each other in the audio range. Even a couple of
| 6MHz crystals 100ppm off would be ~6kHz (temp sensitive), and
| you would need some driving circuits, but you might be able
| to hear the beat by driving an electret microphone or a
| really tiny tweeter coil speaker (probably need an amp
| though).
|
| It's much easier to build/buy electrical rather than
| mechanical LC components to hit audio frequencies
| ~100Hz-10kHz.
| hilbert42 wrote:
| You can get quartz to resonate down to upper audio
| frequencies with certain crystal cuts and manufacturing
| techniques but it's difficult. Typically, the lowest
| frequency in common use is with its use in watches with a
| frequency of 32,768Hz (that's about the lower limit where
| manufacturing and frequency combine to make a useful
| product).
|
| For electronic circuits such as frequency reference markers
| where frequency stability is important the lowest practical
| frequency is 100kHz with 1Mhz preferred, and where frequency
| tolerances are tight 5 and 10MHz are much preferred with
| operation in a temperature stabilized oven to minimize
| frequency drift.
|
| The most frequency-stable crystal cuts are at those
| frequencies, as frequencies increase (say >10MHz to 100MHz),
| which at the highest frequencies require the crystal to
| operate in overtone mode, frequency stability again tends to
| decrease.
| Animats wrote:
| There are piezo buzzers and beepers, of course.
| adrian_b wrote:
| Yes, but those normally just convert the electrical
| oscillations to sounds, they are not parts of the
| oscillators that determine the audible frequency.
|
| In the past, audio RC oscillators or LC oscillators were
| used, with the former being preferred as the latter
| required too bulky inductors to reach so low frequencies.
|
| Nowadays, it is usually simpler to not use any audio
| oscillator, but to use some microcontroller that divides
| the frequency of its clock until reaching the desired audio
| frequency.
| jacquesm wrote:
| Those can make sounds at other frequencies but they are
| _very_ loud on their resonant frequency. Loud enough to
| damage your hearing if you 're unlucky.
| s0rce wrote:
| There are piezo actuators you could certainly feel but not sure
| they are made of quartz, maybe PZT.
| gosub100 wrote:
| And a similar question: if you took a normal magnet and rotated
| it very quickly, say 10k rpm, would it emit an RF signal at
| (10k/60) hz? I'm 95% sure the answer is yes but I've never seen
| this demonstrated.
| hilbert42 wrote:
| 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 wrote:
| > 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| That sinking feeling of knowing you've ground off _just_ a bit
| too much...
| afandian wrote:
| 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 wrote:
| 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 wrote:
| Wow!
|
| I'm working on something much, _much_ smaller than that!
|
| https://blog.afandian.com/tags/harmonium/
| jacquesm wrote:
| You are going to be leveling up in a whole bunch of
| skills.
| afandian wrote:
| Yes! Most important being calibrating what I should and
| shouldn't attempt yet.
| hilbert42 wrote:
| Ha-ha, I didn't read this until I'd written the above
| reply, seems we have something in common.
|
| Incidentally, I'm one of those mad people who'll put on a
| recording of Helmut Walcha playing Bach's Passacaglia and
| Fugue in C minor on a Silbermann and turn the volume up
| until the room shskes.
| adrian_b wrote:
| Adding solder has also been frequently used to correct the
| resonance frequency of quartz crystals that have been
| ground too much, and I mean during industrial mass-
| production, not only in a home-lab setting.
| afandian wrote:
| How are people sticking stuff to quartz? I know less than
| nothing, but the pieces of quartz you find in rock don't
| look like they'd take a solder bond.
|
| I'd assumed that with piezo crystals etc there was a
| mechanical connection rather than an electrode bonded to
| the crystal?
|
| But if you can add solder presumably there is some kind
| of molecular connection with the metal?
| jacquesm wrote:
| There is already a silver patch bonded to the crystal
| where the wire connects to. Adding weight to that
| obviously will not make the load curve any better but if
| you do it with just enough to drop you back down below
| where you wanted to be then it can be a saving move. You
| could also put a trimmer in parallel, but that might not
| have enough range (and can also end up overloading the
| crystal so the oscillator won't start).
| adrian_b wrote:
| Electrodes are deposited on the crystal in vacuum, e.g.
| by metal evaporation or sputtering, in the same way as
| they are deposited on the semiconductor crystals used to
| make transistors or integrated circuits.
|
| The electrodes may consist of multiple layers, a base
| layer that adheres strongly to quartz and a top layer
| that is solderable, e.g. made of nickel or silver.
|
| The pins of the package that hosts the crystal resonator
| are soldered on the electrodes, in places well chosen so
| that they will not damp much the oscillations of the
| crystal.
|
| When the mass of the crystal must be increased to shift
| the resonance frequency, excess solder may be deposited
| on the electrodes.
| afandian wrote:
| Thanks, that's fascinating. I imagine they use a mask and
| large spread? Or a stepper?
|
| Fun video of 'metallization' on a coarser scale!
| https://www.youtube.com/watch?v=e-QcseGvU5o
| hilbert42 wrote:
| Funny you should mention that another hobby of mine was
| rescuing old harmoniums and making them playable again--you
| know, fixing and replacing reeds, renewing bug-eaten felt,
| sealing rat holes in the bellows, etc.
|
| I grant you it's not in the same league as voicing a
| diapason though. :-)
|
| I reckon adjusting and tweaking things goes with the
| territory. I'm pretty much at home tweaking crystals,
| fixing reeds, aligning IF stages in radio and TV equipment,
| there's much of a sameness in the way one tackles all of
| them.
|
| BTW, I've actually repaired reeds by soldering them. Not a
| good fix though as the solder can fatigue with use. Throws
| out equal temperament a bit too but most can't hear the
| difference.
| afandian wrote:
| That's exactly what I'm doing! Nothing grandiose.
|
| https://blog.afandian.com/tags/harmonium/
|
| By 'repaired' you mean closing a fracture? I'm interested
| to hear your experiences! Electronics solder or silver
| solder?
|
| This one is 60 cents sharp across the board (not
| uncommmon), but I wanted a social instrument. So I
| brought them down with solder. The bottom two octaves
| have worked out well. The next two... we'll see. I now
| have the fear that I've weakened the brass by heating it.
| But it still sounds nice and speaks well. Fingers
| crossed.
| gtsnexp wrote:
| This awesome. Could you perhaps remember the title of the book
| you lost?
| hilbert42 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| Thank you!
| hilbert42 wrote:
| _" 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!
| gtsnexp wrote:
| Fantastic! Also found used on abebooks! Thank you
| hilbert42 wrote:
| 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 wrote:
| 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...
| tomcam wrote:
| > according to [2] a train crashed in 1972 due to a badly
| designed crystal oscillator spontaneously jumping to its third
| overtone
|
| New fear unlocked
| jacquesm wrote:
| More interesting: amazing sleuthing to figure out that that was
| the root cause.
| sbinnee wrote:
| Believe or not, when I explained to many non techies how quartz
| watches work and how any computers' hardware clocks work in the
| same principle, they were all surprised how elegant and how
| efficient the mechanism is. I was also impressed when I first
| learned about it. True science and engineering beauty.
| jacquesm wrote:
| Have a look at the company Silicon Time, they make the most
| amazing little devices.
| amelius wrote:
| Could someone take the equivalent circuit of the article and put
| in in CircuitJs to form an oscillator? Thanks!
| jacquesm wrote:
| Nice to see this get more love, I had a fun time going through
| that site, there are lots of gems there.
|
| For instance:
|
| https://www.pa3fwm.nl/projects/sdr/
|
| The longer you read, the more amazed you will be.
| jadbox wrote:
| Dang that fascinating but way above my head. I need to take a
| few classes in signal processing I think to parse what's all
| going on here.
| dilawar wrote:
| Obligatory: https://youtu.be/wHenisSTUQY?si=oNOHR9QRCG3GYvf2
| dilawar wrote:
| Just realised this video is referenced in the article! Didn't
| read it carefully.
| pfdietz wrote:
| I remember when I worked at Motorola some decades ago, there was
| a little section in the factory area in Schaumburg that made
| quartz crystals. It's all long since been sold off (I think all
| the equipment went to China) but I remember all the signs for
| cyanide alarms, presumably due to some step in the manufacturing
| process.
|
| The quartz crystals themselves were grown with carefully
| controlled levels of specific impurities (like scandium) in order
| to reduce their temperature sensitivity.
| adrian_b wrote:
| They may have had baths for galvanic deposition of silver.
| Those typically used cyanide solutions.
|
| Galvanic deposition of silver has been frequently used for
| increasing the thickness of thin metal layers that had been
| deposited in vacuum, in order to adhere to the crystal.
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