[time-nuts] GPS: ADEV or MDEV?

[Dr Bruce Griffiths]

SAIDJACK at aol.com wrote:
>  Hi Bruce,
>   
>  
> in an 'uncontrolled' environment like that one would not get 2-20ppm  retrace 
> on the Zener (as speced in the table sent to this group earlier) I  would 
> think.
>  
> bye,
> Said
>   
Said

Yes it could be worse.
What I'm trying to show is that the thermal environment of the EFC 
reference and DAC is important as is their noise.
Just low pass filtering a PWM waveform whose amplitude is determined by 
a noisy supply regulator, as some do, is just too noisy to obtain 
optimum performance from a 10811 or equivalent performance OCXO.

Of course one can always resort to annealing out the retrace by 
controlled thermal cycling of the reference as Fluke (optionally) do in 
their 7000 series references whenever continuous power is lost.
These 10V references use selected LTZ1000's to achieve a drift of around 
1ppm/year.

Bruce