[time-nuts] Re: MHM-A1 maser temperature stabilization

[Poul-Henning Kamp]

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Skip Withrow via time-nuts writes:

> One issue that I have been up against is the temperature variations of the
> lab location.  The diurnal excursions of the oven heaters were clearly
> visible.  My solution was to build an environmental box (1.5" foam
> insulation board) around the unit 

Apologies for harping about this again:

Please think in terms of thermal impedance!

Look at it as electronics for a second:

You have put a (very big!) resistor between your AC noise source
(the heating) and the sensitive kit (the maser).

Because your resistor is so large, you now have an over-temperature
problem inside your enclosure, which you have tried to mitigate with
a fan.

What you actually need is a low-pass filter with a cut-off lower than 1/24h.

That means /some/ insulation, but not so much that your maser cannot
get rid of the heat it produces, and /a lot/ of thermal mass on the
inside to "short the AC to ground".

This is not magic, and the math is trivial when you already know electronics.

-- 
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