[Elecraft] crystal oven question

[AI4CQ ,James]

A crystal oven consists of a heater in an enclosure for the crystal
and a temperature controller.  To be able to control the temperature
with heat a temperature must be chosen which is above the highest
normal operating temperature which is often more than 100 degrees F.  

A crystal will drift with temperature but for common cuts of crystal
not in a linear fashion.  The AT cut which is most common at HF drifts
in a S shaped plot when plotted temperature vs frequency with the
center of the S near room temperature. Crystals for ovens used in
frequency counters are often specially cut so they are most stable at
the temperature of the oven.   The frequency stability of a crystal in
a crystal oven is determined partly by the drift characteristics of
the crystal but mostly by the accuracy of the temperature control.  

The disadvantage of a crystal oven is it requires power to generate
the heat and it is not suited for portable equipment.  Usually the
oven remains on all the time to avoid warm up which is often more than
1/2 hour.  

AI4CQ James