[time-nuts] OCXO pressure sensitivity before TCXO

[Richard (Rick) Karlquist]

On 8/5/2019 3:30 AM, ew via time-nuts wrote:
> Today most quality OCXO's are in a sealed can but three of the best HP10811, Austron 1150 and OSA 8600/07 are not sealed. Austroon set screw hole has a screw with an O ring. When you try to get the best out of them not part of a loop you may have to consider

The 10811 came in both an unsealed version and a solder sealed version.
The unsealed version is much more common.

When I was working for HP, I tested an unsealed 10811 for
humidity sensitivity. It had a considerable coefficent,
such that I could get more frequency shift by varying
ambient humidity than I could by varying temperature.
Clearly, this sensitivity is all due to the electronics, since
the crystal is definitely hermetically sealed.  This discovery
motivated the development of the bridge stabilized oscillator circuit,
which is vastly less sensitive than the 10811 circuit.

Rick N6RK