One thing that surprised me in the video was when he turn it 180 degrees=20
and the effect increased.  I expected it to go back to 0.  I can see how=20
a crystal on egde could be different from one horizontal, but not=20
different right-sipe up vs upside-down.

I am thinking that there might be a slight temperature gradient in the=20
oven, (hotter at the top) and tilting it or turning it upside-down=20
causes a slight temperature change in the crystal that causes the=20
frequency change.

Kerry

On 8/1/2014 10:22 AM, Sean Breheny wrote:
> I have not yet watched the video in question but gravity has a
> well-documented effect on quartz crystal oscillators. It can usually be
> ignored for all but the most demanding applications but for ovenized
> frequency references which adjust for crystal ageing, it becomes a
> significant factor.
>
> See: http://prc68.com/I/PRS10.shtml#Accel
> and
> http://prc68.com/I/Images/FC_ROT.jpg
>
> It is indeed due to stress created in the crystal, I believe.
>
> Sean
>
>

--=20
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