It is not a matter of skin depth. Skin depth relates to a dissipative
process like EM waves traveling into/through a resistive medium. Soil
and rock are not dissipative to heat in this way. There is a poor
impedance match between the air and the soil but once into the ground,
through soil and rock you can have propagating thermal waves.
David
On 9/27/12 1:07 PM, Alan Melia wrote:
Hi Chris when the British Post Office (later BT) ran radio stations,
the station standard was usually in a hole 30 feet deep. Crystals were
made in our own "Factory", a section of the Research department, so
the crystals would have been cut to suit UK conditions. Maintaining
systems were usually Meecham Bridge and the crystals most probably
Essen rings which are fairly massive bits of Quartz.
Alan
G3NYK
----- Original Message ----- From: "Chris Albertson"
<[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Thursday, September 27, 2012 4:46 PM
Subject: Re: [time-nuts] Low power timekeeping
On Wed, Sep 26, 2012 at 11:05 PM, Hal Murray
<[email protected]> wrote:
As you go deeper you get a delayed history of the surface temperature.
Right. Skin depth.
A good oven runs rings around deep earth stability.
But a hole in the ground doesn't take any power.
That was my point. At some depth you get less then a degree of
day/night and summer/winter variation. That is very good for zero
power input.
Yes a precision controller could do better. I onced used a Peltier
device with water heat sink all running in a vacuum insulated jar. It
kept the temperature pretty much dead-on but at high cost in bulk (55
gal.drum of coolant) and plumbing and in power. But you get 0.3C
error for free and it runs for years on "nothing" It's a trade off.
Chris Albertson
Redondo Beach, California
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