On 2/13/11 8:15 PM, gary wrote:
Two authors come to mind regarding crystal oscillators: Eric Vittoz and
Marvin Ferking. Eric Vittoz is the more modern of the two. His writings
tend towards long term stability of crystal oscillators. Basically, most
designs put too much energy into the crystal, which he claims wears it
out. I'd had to dig up his papers, but my recollection is the failures
were soft (error in frequency) rather than hard (total failure). Ferking
covers temperature stability and crystal pulling.
I haven't dealt with crystal manufacturers in a long time, but my
recollection is the crystal is "tuned" by metal deposition. As you
deposit metal on the crystal, the frequency lowers. Possibly today they
laser trim, i.e. remove metal.
metal deposition is still how it works.
The real unknown is what the frequency will be after aging.. you make a
bunch, run them for a while at higher than normal temperatures, and see
which ones look like decent candidates.
Anyway, I don't think opening up the case
and fiddling with the innards is a good idea.
Back to crystal manufacturers, these companies tend to be pretty small.
when I was working on video chip designs, it was no problem talking to
the CEO or VP engineering. I think it is a capital intensive rather than
labor intensive business. They have a few gurus doing product design and
that's about it.
Bliley is another crystal maker.
But you're right.. there's typically very few people who actually do the
stuff for high performance crystals/oscillators. THere will be a few
techs who have the skills to put the crystal in the holder and seal it
up. A few who make the crystals (running the saws), etc.
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