Hi Nate, I changed the subject as to not further hijack the other thread. Of the 16 captures I collected, some of them included a tuning command (but using the same timed commands I use for other devices such as TwinRx). But, others did not. For example, for the first two data points below (with measured phase difference of -77 and -19 respectively). I simply issued two consecutive timed streaming commands. So, I was very perplexed by the results.
In any event, I plan to re-take the data today both with and without a DDC. Hopefully, if I get rid of the DDC, I will see consistent phase results, but we'll see. Let me know if you have other ideas. Rob On Mon, Jan 27, 2020 at 12:04 PM Nate Temple <nate.tem...@ettus.com> wrote: > > @Rob: With the current init process of the N310, yes it is required to > first set the external LO to 5 GHz. > > With regards to the offsets you're seeing, I believe you should only see a > possible phase difference of 180* within the two channels on the same DB. > Are you issuing a tune request at the start of streaming? > > Regards, > Nate Temple > > On Mon, Jan 27, 2020 at 8:20 AM Rob Kossler via USRP-users < > usrp-users@lists.ettus.com> wrote: > >> Robert, Sammy, >> I am presently running some tests which compare the X310/TwinRx and the >> N310 with regard to channel-to-channel phase. In my setup, I have a signal >> source that is split 8 ways (1:8 splitter) to feed the 4 channels of my >> TwinRx and 4 channels of my N310. I have seen some strange behavior of the >> N310 that perhaps Robert has experienced? Take a look: >> >> - For the TwinRx (for which I am a more experienced user with LO >> sharing), I get consistent channel-to-channel phase difference among all >> channels. This is true regardless of power cycles, re-starts of UHD, etc. >> - For the N310 (for which I am a beginner when it comes to external >> LO operation) >> - it seems more complex to run in this mode (as compared to >> TwinRx). In order to get it to work, I have had to disable startup QEC >> calibration because it seems that the N310 initial cal occurs at 2500 >> MHz >> RF such that I would need to have my external LO at 5000 MHz for >> startup >> (during the UHD deveice 'make') and then later switch my external LO >> to the >> desired RF*2. Is this true? >> - when I run with either external LO or internal LO, I see >> inconsistent channel-to-channel phase results even between the two >> channels >> of a given daughterboard that share the same LO. I do not understand >> how >> this is possible. My results over 16 captures (with some re-starts of >> UHD, >> device reboots, and switching between internal/external LO) show the >> following channel-to-channel phase difference between channels 0 and 1 >> which share the same LO: (values in degrees) -77, -19, -77, -19, -77, >> -19, >> -19, 39, -19, -19, -77, -19, -77, 39, -19, -19. Note that there are >> only 3 >> unique values and the delta happens to be 58 deg, but I don't know what >> that implies... >> >> Rob >> >> >>
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