[time-nuts] GPS: ADEV or MDEV?

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Apr 23 21:53:27 EDT 2007


SAIDJACK at aol.com wrote:
> Hi Tom,
>  
> BTW: the retrace hysterisis of typical very high-quality OCXO's is speced  at 
> 1E-08 (24 hours off, 2 hours on) that's probably a lot worse than the voltage 
>  reference zener retrace will be.
>  
> A typical 20ppm Hysterisis on a 5V Zener with the OCXO having a +-22Hz  
> (0-5V) adjustment range gives 4.4E-011 retrace. Several orders of  magnitude better 
> than these particular OCXO's inherent retrace by  itself. 
>  
> bye,
> Said
>   
Said

If an unheated reference exposed to wide ambient temperature swings is 
used then hysteresis may be significant when the OCXO is continuously 
powered.
The significance and magnitude of the effect depends on the range of 
ambient temperature variations experienced.

Bruce




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