Adding mass increases the thermal capacitance adding insulation
increases the thermal resistance.
It is possible to construct an enclosure with a long thermal time
constant together with relatively low thermal resistance so that the
temperature of a GPSDO or similar device within the enclosure only
increases by a relatively small amount.
Multiple alternating layers of thermal conductor and thermal insulator
reduce thermal gradients as well as temperature fluctuations.
Having an outer conductive layer reduces the temperature gradients over
the insulator surface.
Readily available inexpensive aluminium foil is a cheaper alternative to
expensive noble metal foils.
Silica aerogel is one of the most effective insulators.
Balsa wood has been used as the insulator in portable temperature
controlled ensclosures for standard cells.
Bruce
And the amazing thing is that this temperature control double
oven technology for oscillators was well advanced in 1931. See:
http://www.leapsecond.com/museum/gr676b-50kc/
and especially the "temperature control apparatus" patent:
http://www.leapsecond.com/museum/gr676b-50kc/US1967185.pdf
/tvb
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