Skip Withrow's writeup is very interesting. As Skip mentioned, the Trimble NetRS is a survey-grade dual frequency GPS receiver which accepts a 10 MHz clock input.
It appears that the US Coast Guard has recently replaced a large number of these NetRS units, and sent the old ones to surplus. They are now appearing on eBay for approximately the price of a Thunderbolt (they used to be several times higher). This situation probably will not last. It seems possible to use a NetRS, plus an OCXO and an external computer such as a Raspberry Pi, to build a dual-frequency GPSDO which would be immune to ionosphere effects. It seems possible to extend such a system by running RTKLIB on the external computer, fed with global GPS correction data from ITRS via NTRIP, to build a GPSDO with PPS precision of a few nanoseconds. Implementation is left as an exercise for the reader (but see Ole's hints at https://www.efos3.com). Cheers! --Stu _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.