[time-nuts] Re: Project Great

[Bob kb8tq]

Hi

All these devices *can* be sensitive to the environment. What degree of 
sensitivity they have is a function of how “nutty” one went on this or that
design. It also is a function of things like cost, size, and power consumption. 

The target market for things like the 5071 is a “we can afford it” sort of 
crew. Even today various government agencies from various countries 
buy the bulk of the 5071’s produced. Yes sorting this out is a bit complicated.
Multi step procurement is pretty common. 

Telecom Rb’s and OCXO’s normally go into a *very* different market. There
is indeed a “good enough” point at which the willingness to pay goes away. 
Temperature stability is one of many things that could be better if more 
money / power / volume was thrown at the problem. 

So no, not a simple single answer.

Bob



> On Nov 29, 2021, at 9:55 AM, Lux, Jim <jim at luxfamily.com> wrote:
> 
> On 11/29/21 1:57 AM, Hal Murray wrote:
>> jim at luxfamily.com said:
>>> And a lot ofsources may have a low flat spot in the curve, but it
>>> eventually trends up. Except for primary standards like Cs beam.
>> What's magic about "primary standard" or "Cs beam" that keeps the ADEV from
>> trending up?
>> 
> Their ultimate accuracy is dependent only on a invariant physical property that is independent of time.
> 
> A quartz crystal ages. No matter how good your oven is, the frequency will change over a long time.
> 
> Mercury ions, Cs ions (perhaps all ions?) have frequencies that are a fundamental property of the ion.  There might be practical implementation limits or side effects that limit the lowest achievable uncertainty - hot atoms will have higher variance than cold atoms, for instance. So not all Cs primary standards have the same ultimate performance.
> 
> 
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