# Does the frequency of a crystal influence its height?

Here is a picture of two crystals:

Does the difference of frequency explain why the 6Mhz crystal on the right has a lower profile than the 5Mhz one ?

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Technically - the height influences the frequency, I doubt that the frequency influences the height (much) :-) – Toby Jaffey Apr 8 '10 at 15:56
These are crystals, not crystal oscillators. – starblue Apr 8 '10 at 18:33
@starblue: thanks for pointing this out... edited questiong accordingly. – JonathanD Apr 8 '10 at 20:02
I doubt there is a relationship. I'd like to know why there are two different sizes, though. Anyone have a picture of one of these opened up? – endolith Mar 12 '11 at 4:43

Influence, yes. Determine, no. For example, here's selection of shapes and sizes for the same spec crystals (and some ceramic resonators...)

The frequency is determined by the size, shape and cut of the quartz crystal inside the package, as well as where the electrodes are placed on it.

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Can you fix the image please. – Dean Aug 13 '12 at 20:42
I'm having a hard time believing those yellow things are crystals. They look like ceramic resonators. – gbarry Aug 13 '12 at 21:21

There seems to be a confusion between the size of a (quartz) crystal package, and the crystals' physical properties which include the crystal's size and it's resonant frequency due to its piezoelectric properties.

In your photo, the crystal on the left appears to be a very common HC-49/U package size. The one on the right is most likely an HC-49U/S.

From ICM, a crystal manufacturer, "The frequency is a function of the thickness of the crystal. By carefully polishing or lapping a crystal, it can be made to oscillate at any frequency." (source) In fact, amateur radio radio operators ("hams") historically were known to polish surplus crystals to their desired frequency, back when the cost of manufacturing was much higher. The practice was sometime referred to as "rock grinding." (ref one & ref two)

You can verify this by looking at a manufacturers' specifications for crystals in different packages.

E.g. FOX through-hole crystals and ICM, where in fact the larger package includes overtone crystals (page 3, PDF) for higher frequencies (looking at HC-49/U and HC-49/S). At fundamental frequencies they are often the same frequency range available.

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And the size of the crystal! With the usual AT-cut crystals the size is inversely proportional to the frequency - low-frequency crystals are larger than high-frequency ones.

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Hi Leon. Just to be a little pedantic, that would be inversely proportional ;-) – Ian Apr 8 '10 at 13:18
Leon, [this page][1] suggests the opposite: higher frequency crystals are only available in larger packages. What do you think ? [1]: icmfg.com/thruhole_crystals.html – JonathanD Apr 8 '10 at 15:56
@Jonathan - The higher frequency crystals - above 25MHz - are often driven at harmonic frequencies above the fundamental frequency. Further, larger crystals also can be driven at higher power so the harmonic frequencies can be more easily selected for. What this means is that sometimes for some uses a higher frequency crystal is actually larger than a lower frequency crystal driven at its fundamental frequency. Note the operational mode and max ESRW in this table as the frequency goes up: icmfg.com/crystal_hc49u.html – Adam Davis Apr 8 '10 at 18:30
Ian is correct, of course. I should have said inversely proportional – Leon Heller Apr 8 '10 at 19:27
@Adam: thanks for that informative comment! – JonathanD Apr 8 '10 at 20:03