Bob,
Many OCXOs, and definitely the CMAC (now RAKON) STP2145A, use ambient
compensation technology. It is not possible to place the heater, the crystal
and the temperature sensor in exactly the same place, and consequently there
will be a thermal profile within the OCXO which depends on the oven design
and the external environment. The ambient compensation corrects for this
effect. (The temperature is measured inside the unit in two places in order
to determine the thermal profile, and a calibrated amount of this
differential measurement is used to correct the oven control).
If, by lagging the OCXO, you change the thermal profile, which you will, the
internal compensation set during calibration will be compromised. This will
make the OCXO more sensitive to changes in ambient temperature than it
should be.
Whilethis may not apply to double-oven oscillators, I still don't beleve it
is a good idea to lag them.
You achieve nothing useful by reducing the power consumption of the OCXO
through lagging: place the OCXO where it can have modest convection, but no
draughts or insulation, and preferably no undue heating from the nearby
equipment.
73,
Murray ZL1BPU
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