Your time offset is in line with the time offset we are seeing in our N310's. I think this is because TX 0, 1 is on one RF chain (with its own local oscillator) while TX 2, 3 is on its own RF chain with a separate LO.
As far as time delay or how long it takes for the RF components to warm up TX 0,1 and TX 2,3 might as well be entirely separate devices? Not sure if my thoughts are logically sound though. On Thu, Nov 8, 2018 at 3:29 AM Serge Malo via USRP-users < usrp-users@lists.ettus.com> wrote: > Yes: we are using UHD 3.13.1.0 RC1, with the latest file system image > > I can try to use lower tx start times to see if the time offset changes > with that. > > Thanks, > Serge > > On Wed, 7 Nov 2018 at 21:44, Marcus D. Leech <patchvonbr...@gmail.com> > wrote: > >> On 11/07/2018 09:31 PM, Serge Malo wrote: >> >> Yes: >> We only use one streamer for all RF outputs, and send time_spec with each >> call to the streamer's send method. >> We reset the internal time with set_time_unkown_pps(0), and program the >> first samples to be streamed at a time of 0.800s. >> It is basically the same code we used on the X300/X310. >> >> Thanks, >> Serge >> >> Well, that is quite strange--the magnitude of the time offsets is larger >> than I would expect. >> >> Perhaps someone from the N310 team can comment? >> >> Serge, are you using the latest UHD and system image versions for the >> N310? >> >> >> >> On Wed, 7 Nov 2018 at 21:03, Marcus D. Leech via USRP-users < >> usrp-users@lists.ettus.com> wrote: >> >>> On 11/07/2018 08:53 PM, Serge Malo via USRP-users wrote: >>> >>> Hi all, >>> >>> We are trying to send 4 synchronous signals from the 4 Tx ports of the >>> N310. >>> We are using UHD 3.13.1.0 RC1 under Ubuntu. >>> Central Freq = 1575.42 GHz and 1227.6 MHz >>> Master Clock rate = 153.6 MHz >>> >>> We would expect to have less than 3ns offset between all TX ports of the >>> N310, like we do with the X300/X310. However, we have measured 4700ns >>> between TX RF ports 0 and port 2. >>> We have tried the next things with no more success: >>> - Sampling rates of 25.6MSps, 38.4Msps, 76.8Msps >>> - Init with the device options "init_cals=ALL" and "force_reinit=1" >>> - Use the internal GPSDO >>> - Use clock_source=external and time_source=external (from an Octoclock). >>> >>> Can you tell us: >>> -What time offset between TX RF ports we should expect to achieve? >>> -Is there anything else we can try to reduce this offset to less than >>> 3ns? >>> >>> Best regards, >>> Serge >>> >>> >>> How are you setting up your TX streamer? Is it time-tagged to start at >>> a particular device time? >>> >>> >>> >>> _______________________________________________ >>> USRP-users mailing list >>> USRP-users@lists.ettus.com >>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>> >> >> _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >
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