[time-nuts] Improving the stability of crystal oscillators

[Brooke Clarke]

Hi Bruce:

All the papers are for depths on the order of a few feet, aimed at plant 
growth, nevertheless in all cases the temperature was changing by at least 1 
deg c at the deepest depth recorded.

I've heard there is some depth that building foundations need to be so they 
don't get winter frost heave that might be on the order of a couple of feet, 
but that's far different from an constant temperature depth.

I'm guessing that 10 or 15 feet may be required to get fractional degree temp 
stability where I am.  The Wisconsin data was in loam which I think means a 
fairly good insulator.  They had the widest temperature variation (15 c delta @ 
120 cm down).  I've got sand and clay after the first foot or so which may be a 
better thermal conductor implying less variation.

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam


Bruce Griffiths wrote:
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+brooke=pacific.net at febo.com RETRY
> 
> Brooke Clarke wrote:
> 
>>Hi Bruce:
>>
>>Details on your experiment please.
>>Hole/pipe diameter, material?
>>Depth?
>>Delta T at different depths vs surface ambient?
>>Soil type?
>>
>>
>>Have Fun,
>>
>>Brooke Clarke
>>  
> 
> Brooke
> 
> Unable as yet to find my data, it was published in some very obscure
> publication if I remember correctly.
> However there was extensive series of records kept in England from the
> time of Lord Kelvin.
> 
> More recent data is available from the US forest service among others:
> http://ncrs.fs.fed.us/pubs/rn/rn_nc032.pdf
> Above is for Wisconsin, not directly applicable to California.
> http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?letter=.&classic=YES&bibcode=1952AuSRA...5..303W&page=&type=SCREEN_VIEW&data_type=PDF_HIGH&send=GET&filetype=.pdf
> <http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?letter=.&classic=YES&bibcode=1952AuSRA...5..303W&page=&type=SCREEN_VIEW&data_type=PDF_HIGH&send=GET&filetype=.pdf>
> Above paper by CSIRO is for an Australian site.
> Analysis is fairly comprehensive.
> 
> http://www.mmm.ucar.edu/mm5/lsm/soil.pdf
> 
> http://www.ias.ac.in/epsci/mar2002/Esb1439.pdf
> 
> Bruce
> 
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