My Rubidium reference vs my GPSDO.
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=979920;image)
I probably need to find a cesium reference to know who's right and who's not.
Isn't GPS controlled by NIST & space rubidium oscillators?
don't think so. the master clock for gps used to come from the us naval observatory.
maybe it changed?
It's still USNO but, of course, since UTC and GPS time are sort of related, (it's complicated) there's some steering and interaction with both NIST and BIPM. They do not exist in a void. Professional time-nuts have conferences and stuff.
IIRC the satellites fly Cs clocks, which are steered from USNO.
Since we have no domestic GNSS system in Sweden, we've decided to build a terrestrial system instead, with NTP and PTP being the prime methods of distribution. In 4, soon to be 5, locations around the country, time servers are located in bunkers, and connected to the Internet where they serve UTC(SP) to anyone who wants it via NTP and PTP to those who need that, albeit for a fee.
I'm no proper time-nut, but I know people who are professional time keepers.