[time-nuts] Low-Cost Rubidium Performance

Chris Albertson albertson.chris at gmail.com
Fri Feb 10 02:19:27 UTC 2012

Let me strengthen the argument below.   Let's say you are building and
selling Rb units to the telcom industry and you've spec'd your product
for use in the range of -25C to +85C.   Now you want to include an
ADEV plot in your sales literature.  Should you place the unit in an
environmental controlled box while you measure it?    I think you'd be
accused of fraud if you did not state that the plot is not
representative of the full temperature spec.   I think in order to be
valid you always have to state the test conditions but you can use ANY
test condition,  Place it outdoors, in a lab or what ever but just say
what you did and then your plot has meaning.  I think the converse to
true, that without knowing the test conditions the plot is little

> Why? Unless the unit is spec'd for use only at a constant temperature,
> temperature variations are something it needs to deal with, and should be
> included in any measurement of how good it is. In what way is temperature
> variability special, that it shouldn't be included in ADEV measurements, but
> all other contributors to variability should be? Certainly, there may be a
> large non-random component to temperature (diurnal, annual, in many
> environments), but there's also a significant part which is random - should
> you somehow correct for one, but not the other?
> Shouldn't one expect the ADEV be better for a double oven OCXO than for a
> bare crystal?
> The only issue I see is it may make fair comparison difficult, unless units
> are compared under identical conditions.
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Chris Albertson
Redondo Beach, California

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