Yes, running everything chilled would be better if low temperature
crystal turnovers were available. It is more complicated to chill
than heat, of course, even today, but way back when they started
temperature stabilizing things it was nearly impossible on a small
scale - or at least very impractical, until the advent of TECs. It's
also trickier to do both because there's that crossover region where
the mode has to shift and you can get dead zones in the control
function. Doing heating or cooling only is like a Class-A amplifier -
much simpler to keep linear.
I think the main problem with chilling though, is that you get
condensation, depending on the humidity (or dewpoint), so you can't
go very low in temperature to take advantage of lower noise and
bias/leakage currents in devices, without encountering the
condensation problem. For example, one of my projects involves making
a very stable voltage standard that has the guts inside a TEC-chilled
(or warmed) aluminum block. I plan to run it somewhere around 15-20
deg C or so, or as low as I can without having condensation under
most conditions, since the guts aren't going to be hermetically
sealed inside (but maybe have a rechargeable dessicant). Another
project involves building a log attoammeter with the input amplifier
TEC-chilled as far down as possible (-40 to -50 deg C or so) to
minimize bias current. This one has to be specially guarded, and with
the cold block inside a hermetically vacuum sealed enclosure, as any
condensation whatsoever - inside or out - could defeat the whole purpose.
Ed
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