[time-nuts] new clock

Neville Michie namichie at gmail.com
Wed Jul 23 09:22:48 EDT 2014


Deep soil temperature stability is a bit of a myth, mainly because not many people actually measure it.
I measured a beautiful 0.2C degree annual sine wave 15 metres down in limestone in Kentucky.
The catch is the Gauss's Error function drop-off rate of temperature fluctuation is a very 
good low pass filter, so all the ambient noise of longer than a year period is not well
attenuated. Secular variations, like a warm winter, a warmer than normal decade, all appear
with less attenuation. 100 year functions reach 100 metres depth, and that does not count effects from 
percolating ground water.
Admittedly a deep cellar made a good clock vault, but a thermistor, a computer fan and 
a 100 watt filament lamp in a wooden box can give far more accurate temperature control.

cheers,
Neville Michie


On 23/07/2014, at 10:17 PM, Alexander Pummer wrote:

> it does need a different design, but a buried oscillator, 5 to 8 meter deep in the garden has the best temperature stabilization, just don't turn thee power off, but that could be done using the old Greek water-clock principle, the spill over stabilizer. In the Bay Area [California] the soil's temperature is around the year approximately 17C° ±0.01C° if you go further down it will be even more constant, without any heating power and control loop....
> 73
> KJ6UHN
> Alex
> On 7/22/2014 6:43 PM, Bob Camp wrote:
>> Hi
>> 
>> A lot depends on the oscillator. My fine old GR rack mount took most of 9 months to settle most of the way. It was still dropping in a year after that when I stopped watching it. Some of my T-Bolts took a week, some took a couple months….
>> 
>> Best thing you can do with any OCXO is just leave it on power.
>> 
>> Bob
>> 
>> On Jul 22, 2014, at 7:53 PM, paul swed <paulswedb at gmail.com> wrote:
>> 
>>> Agree with Marks comments.
>>> Regards
>>> Paul
>>> 
>>> 
>>> On Tue, Jul 22, 2014 at 5:25 PM, Mark Sims <holrum at hotmail.com> wrote:
>>> 
>>>> An oscillator can take many weeks to settle in after being powered off /
>>>> shipped / abused / looked at cross-eyed / etc.   It typically takes a
>>>> Thunderbolt a month or two to  settle down after being shipped from China.
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