In article ,
Tim Wescott wrote:
[....]
Overtone crystal cuts are not fundamentally different from fundamental
crystal cuts, so to a 1st-order approximation they'll work. Crystals do
have spurious responses that can cause mode jumping, and these responses
don't necessarily map the same way the overtones do, so using a 20MHz
crystal at 100MHz may or may not work, depending on the luck of the
draw. Other than that I don't know of any differences.


There is a whole science of crystals all on its own. When they make a
crystal they make a thin disk of material. You would normally expect the
edge of the disk to simply be at right angles. Instead it looks like
this:



***********************
*
*
*
*
*************************

The exact angle and depth of that chamfer is how they control which
overtones are selected for and which are supressed. In fundamental
crystals, the maker usually grinds the chamfer so as to reduce the 3rd
harmonic responce.


--
--
forging knowledge