[time-nuts] Re: Primary frequency standard

[Richard (Rick) Karlquist]

At HP, it was explained that a primary standard
could be built on a desert island containing no
frequency standards nor any GPS receivers, etc.
and it would be guaranteed by design to meet its
spec.  It could have adjustments, either operated
by a technician or a computer controlled algorithm,
but none of them consisted of "setting" the frequency
to the correct value using a frequency counter, etc.

It isn't based on accuracy.  The reduced performance
HP 5062 is still primary, even though the 5061 is more
accurate.  Similarly, the 5071 is still more accurate,
but the 61 and 62 retain their primary status.

ADEV is not an issue to qualify for primary status.

Rick N6RK

On 3/26/2021 2:42 PM, cdelect at juno.com wrote:
> In reference to:
> 
> "It would be cool to say one has a "primary standard", .... So, I think
> we should be careful with the term, it's get thrown around too lightly."
> 
> Any of the hobby grade used Cesium standards is actually a Primary
> frequency standard as it does meet the definition of:
> 
> A frequency source that meets national standards for accuracy and
> operates without the need for calibration against an external standard.
> 
> They ARE able to meet their accuracy specs without calibration against an
> external standard.
> 
> The definition does not exclude them.
> 
> I realize that Metrology usage may be different but the definition makes
> no judgement as to how performance levels!
> 
> Cheers,
> 
> Corby
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