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@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
