Poul-Henning wrote:
PLLs are really not that hard [context: we have been discussing all-digital PLLs ("ADPLLs")]
Yes, I know -- I have designed more than a few. I have also reviewed more than a dozen hobbyist designs and modeled some of them, and found that few hobbyists seem to have mastered the art. Judging also by on-list responses over the years, it does not appear that many time nuts are interested in designing and building their own ADPLLs. So, I conclude that disciplining a good OCXO with GPS and getting the best stability the OCXO can deliver is not practicable for most hobbyists.
The OP in this sub-thread indicated that he was considering using an LTE-Lite to discipline a "really good" 10811, and it appeared that his expectation was to end up with a GPSDO more or less as good as his 10811. My point was simply to put realistic bounds on the expectation.
Said posted that a quick lash-up with an OCXO produced stability about 10x better than with the on-board TCXO. That is a useful improvement, but a good OCXO (certainly, a "really good" 10811) will have stability about 3 orders of magnitude better than a TCXO (1000x), so two decades of possible improvement were not realized.
Said's experiment was a proof-of-concept exercise and not a careful optimization, so it is almost certain one could do better than 10x with some further work. But I very much doubt that optimization can gain the entire two decades of potential improvement (short of designing a full ADPLL, in which case you don't need the LTE-Lite at all -- all you need is a source of PPS), and I doubt it is possible to gain even one whole decade.
So, I am inclined to think that there are better (and easier) ways to discipline a 10811 to reach its ful potential, that's all.
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.
