[time-nuts] Commercial software defined radio for clockmetrology

Kevin Rosenberg kevin at rosenberg.net
Sun Jul 31 23:05:14 EDT 2016


Hi Tom,

Thanks for your thoughts. I had looked at your helpful page when I started researching the effects of averaging. Currently, I’m experimenting with the dual receivers in the SDR using cross-correlation to reduce the noise floor.

Kevin
 
> On Jul 30, 2016, at 5:08 PM, Tom Van Baak <tvb at LeapSecond.com> wrote:
> 
>> SDRs sample at high rates. The slowest the USRP N2x0 can sample is just under 200Ksps.
> 
> Hi Kevin,
> 
> I don't have an easy answer for you. BobC / BruceG / MagnusD / JohnM / EnricoR can shed light on this. But I support your effort to figure out how to obtain real truth from a massive oversampled data set.
> 
> If you feel uneasy that ADEV statistics might lie, see: http://leapsecond.com/pages/adev-avg/
> 
> ADEV is always a tricky, since the measurement bandwidth is not always specified, or how that bandwidth is implemented. Both the front-end h/w design and any embedded s/w manipulation of raw data will distort (bias) the statistics. Distortion itself is not a show-stopper, as long as you can properly model it and back it out. But it seems the challenge is knowing how valid the model is, and if model itself depends on the noise type.
> 
> /tvb
> 
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