[time-nuts] Improving the stability of crystal oscillators
bruce.griffiths at xtra.co.nz
Sat Oct 13 21:19:29 EDT 2007
Brooke Clarke wrote:
> Hi Bruce:
> I've also looked into drilling a hole (garden hose, 90 deg fitting & pipe with
> end smashed flat to make a nozzle will easily drill as deep as the pipe is
> long). Then using a short length of capped copper pipe at the bottom and the
> rest PVC.
> Like I think here in California wine country 4 feet would be plenty deep. But
> this method only works at your home location. Not too good for a clock that
> will be sent to someone else.
> I think the long time constant method can be done in a few cubic inches.
> Have Fun,
> Brooke Clarke
The required depth depends on the soil diffusivity and the temperature
It is instructive to install thermometers at depth intervals of a foot
or so and record the temperature fluctuations experienced by each
This was first done around 1860 by Forbes.
I repeated the experiment in 1966.
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