It is definitely regenerated, and I can believe that there's no compensation for delay. I haven't measured the output on a phase noise analyzer, but as it's coming from the same clock generator which provides the sample clock for the device I would expect it to be similarly clean.
Nick On Tue, Oct 16, 2018 at 9:07 AM Marcus D. Leech <mle...@ripnet.com> wrote: > On 10/16/2018 12:00 PM, Nick Foster wrote: > > Wait, what? I've been using REF OUT for years now. What am I missing? What > does "aren't actually fully supported" mean? > > My understanding, and R&D can correct me if I'm wrong, is that the REF OUT > not only has no phase-length compensation, but it's > a regenerated signal with unpleasant phase-noise. > > But if those issues have been addressed, then I retract my statement. > > > > On Tue, Oct 16, 2018 at 8:57 AM Marcus D. Leech via USRP-users < > usrp-users@lists.ettus.com> wrote: > >> On 10/16/2018 07:44 AM, Francois Quitin via USRP-users wrote: >> >> Dear all, >> >> >> >> We encountered a small problem when we try to build a 4-element MIMO >> array with two X310 (equipped with UBX daughterboards). We are working on >> UHD-3.10.3: >> >> - When we use an octoclock to provide the 10 MHz Ref and the >> PPS to both X310, the phase of each receiving front-end stays nicely >> constant (see octoclock.png). The Ref Source and Time Source are set to >> “external” in GNU Radio (the points represent a measurement taken every ten >> seconds) >> >> - When we use the 10 MHz Ref Out and PPS Out from one X310 and >> feed it to the Ref In and PPS In of the other X310, we observe a drift in >> the phases of the channels from the second X310. This is shown in the graph >> daisyChain.png, where we take one point every ten seconds. We configured >> GNU Radio to set the Ref Source and Time source of the first USRP to >> “default”, the ones of the second USRP to “external”. >> >> >> >> This drift is something more severe, sometimes less, but it’s always >> present. Any idea why we observe this? >> >> >> >> Many thanks, >> >> >> >> François >> >> >> >> --- >> >> Francois QUITIN >> >> Assistant Professor >> >> >> >> BEAMS Dpt. – Embedded Electronics >> >> Brussels School of Engineering >> >> Université Libre de Bruxelles (ULB) >> >> >> >> Web https://sites.google.com/site/fquitin2/ >> >> Phone +32 2 650 2829 <+32%202%20650%2028%2029> >> >> >> >> The REF OUT and PPS OUT ports aren't actually fully supported in the FPGA >> code, and we don't, at this point, recommend their use. >> >> >> >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> > >
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