On 10/31/17 1:47 PM, Bob kb8tq wrote:
HI

TCXO is a very loosely defined term. A part that does +/- 5 ppm -40 to +85C
is a TCXO. A part that does +/- 5x10^-9 over 0 to 50C may also be a TCXO.

Dividing the total deviation of either one by the temperature range to come
up with a “delta frequency per degree” number would be a mistake. You
would get a number that is much better than the real part exhibits.

Working all this back into a holdover spec in an unknown temperature
environment is not at all easy.


Very much so - most of the TCXO curves I've seen tend to be "much" better than the spec over the central part of the frequency range (which makes sense, the underlying crystal is a cubic with temp, most likely)

Retrace and hysteresis might be your dominant uncertainty.
I've attached a typical TCXO data plot for your viewing pleasure..
(that's an expensive oscillator, because it's for space, but I don't think space or not changes the underlying performance)


Bob


Attachment: TCXODataVectron 47.pdf
Description: Adobe PDF document

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