[time-nuts] Last Call Group Buy Ublox LEA-6T

Bob Camp kb8tq at n1k.org
Thu May 19 00:34:43 UTC 2016


Hi

While it may not be the only parameter worth considering: 

The standard deviation of the delta between adjacent pps outputs goes down to below 500 ps on the LEA-6T when sawtooth is applied. 

Bob


> On May 18, 2016, at 7:23 PM, Charles Steinmetz <csteinmetz at yandex.com> wrote:
> 
> Bert wrote:
> 
>> Our first tests are with a 500 ps
>> DS  chip because I did have them, but  200 ps will work with a T5 or 6. We
>> are  also considering using two Micrel SY 89295UTG in series with 10 ps
>> resolution,  but with the limitation of a single frequency GPS receiver and
>> ionosphere delay  variations one has to ask does it make sense?
> 
> Think first about what the GPS engine has to work with -- nothing but the timing generated by its current GPS timing solution.  It seems very doubtful that sub-nS accuracy is possible.  This provisional conclusion is supported if we look at commercial GPSDOs using single-frequency GPS engines and sawtooth correction (or using local oscillators that divide evenly by 100nS, like the Tbolt).  The best commercial units seem to place the PPS within 5nS or so on a routine basis.
> 
> So, even 500pS appears to be considerably better than necessary, given the limitations imposed by the timing engine, atmospheric dispersion, and the GPS system.
> 
> Best regards,
> 
> Charles
> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.




More information about the Time-nuts_lists.febo.com mailing list