[time-nuts] Different Thunderbolt versions

[Bruce Griffiths]

Said

The other thing to consider is the noise in the built in FS725 PPS error
measuring system.
Whilst the resolution is 1ns it isn't that accurate and its instability
may also be worse than this.
Internal resolution may be as high as 200ps.

Bruce

SAIDJACK at aol.com wrote:
> Hi Bruce,
>  
> the PRS-10 datasheet is pretty smart in not showing the data below 10s  
> through, it would make their >10s performance not shine as much. There  certainly 
> could not be any measurement reason for not showing <10s  ADEV.
>  
> As someone has mentioned, they also used a very bad GPS receiver as a  
> reference which makes their ADEV look spectacular against the GPS  ADEV.
>  
> It is possible that this plot is pre-SA-disabled, but then should they not  
> update their website with more recent data? I guess one could also argue that  
> even if you use a bad GPS the unit will still generate a good ADEV above 10s  
> intervals and that is what they are trying to show. It's all in the  
> specmanship.
>  
> bye,
> Said
>  
>  
> In a message dated 2/25/2009 23:04:54 Pacific Standard Time,  
> bruce.griffiths at xtra.co.nz writes:
>
> That  isnt a great advantage in this application given that the
> contribution of  the ionosphere to the VLBI receiver output signal phase
> noise is around  8E-11 @ 10s at 50MHz.
> Typically in VLBI integration times op up to 10,000  seconds or more are
> used. Integration times shorter than 100 sec are not  usually of  much
> interest.
>
> Bruce
>
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