Hi How close are you trying to get?
How far apart are the GPSDO’s? A “run of the mill” number would be out around 100 ns. A “pretty good” number is in the 20 ns range. A “crazy good” number would be 2 ns. To do better than this, you likely would need to go to a more exotic configuration on the GPSDO. Bob > On Mar 6, 2022, at 12:55 PM, Krishna Makhija <km...@virginia.edu> wrote: > > Hello, > > I am new to the whole precision time-keeping game (and to this mailing > list) so I apologize in advance if my question is too naive or has been > answered already in your mailing list. > > Is it possible to have two separate GPSDOs, each with their own antennas, > be phase coherent to each other? I have a Jackson-Labs Fury > <https://www.jackson-labs.com/index.php/products/fury> and a Mini-JLT > <https://www.jackson-labs.com/index.php/products/fury>. I am using each to > provide a 10 MHz reference to two separate software-defined radios (SDRs). > In my tests I find that the phase offset between said SDRs has a slow > time-varying behavior. I know the frequency errors of the GPSDOs are of the > order of parts per trillion which will show up as slow time-varying phase > offsets but I was hoping to use the PPS offsets and instantaneous frequency > errors that I get from these modules (using SCPI commands) to be able to > "back out" or predict what that time-varying phase offset would be. Is such > a thing possible? Currently, the time-varying phase change does not seem to > follow any discernible pattern and my attempts at backing out the phase > change do not match my measurements. > > Here is the math I am using for calculating what I *think *the phase > *should* be: > [image: image.png] > [image: image.png] > > [image: image.png] > Does any of this seem sensible? Any input is appreciated. > > TL;DR: Trying to get phase coherence between two separate GPSDOs may not be > possible but can you use PPS offsets and frequency errors metadata to > correct for it in post? > > Regards, > Krishna > <image.png><image.png><image.png>_______________________________________________ > 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. _______________________________________________ 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.