[time-nuts] Looking for Wavecrest Visi

[Dr Bruce Griffiths]

SAIDJACK at aol.com wrote:
>  
> In a message dated 4/7/2007 04:08:20 Pacific Daylight Time,  
> cfmd at bredband.net writes:
>
>
> The  Wavecrests are wonderful tools, but they address a different problem  
> than
> what normal time-nuts usually care about, so they are not a given  perfect
> counter for long term comparision. It is aimed at jitter. 
>
>
> Hi Magnus,
>  
> that's true for the SIA/SRT series of Wavecrest instruments.
>  
> But the DTS series (DTS-2070, 2075 etc) have features that your SRT does  not 
> have, for example cable-length measurement with picosecond resolution.
>  
> The DTS units also have sophisticated external Arming features the SRT  
> doesen't have (two ARM inputs).
>  
> They also have A to B time intervall measurements so one can do a DUT to  
> Cs/Rb comparison for example with +-25ps accuracy per measurement, at 40000  
> measurements per second. Visi allows long-term high-resolution drift plots that  
> can be turned into ADEV plots.
>  
> Theoretically, this means +-25E-012 / rt(40000) = +-1.25E-013 measurement  
> accuracy per second if it's internal accuracy-noise is gaussian (I am not sure  
> it is)  so it would average out when comparing one 10MHz against  another 
> 10MHz source.
>  
> I don't have the Visi software so I cannot use the HiPer 40Ks/s option so  
> the above remains theory until I can find the software.
>  
> Also, I don't think the SRT3000 can do two-input A to B  measurements if I 
> remember correctly.
>  
> As of today, there is a DTS-2070 on Ebay (search for "Wavecrest Digital  Time 
> System") for $900 buy-it-now from a known-good vendor.
>  
> In summary, I think the SRT is perfect for many-input parallel jitter  
> analysis, while the DTS is more of a traditional time-intervall-analyzer  suitable 
> for time-nuts usage. BTW: I think they both are not very good as true  
> frequency counters.
>  
> bye,
> Said
>
>
>
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>   
Said

Your theoretical resolution seems somewhat awry see:
http://www.femto-st.fr/~rubiola/conference-articles/2005fcs%28rubiola%29-counters.pdf 
<http://www.femto-st.fr/%7Erubiola/conference-articles/2005fcs%28rubiola%29-counters.pdf>

Bruce