Sorry typo. I did use a frequency of 3.51GHz. > On 5 Dec 2018, at 12:54, Marcus Müller <marcus.muel...@ettus.com> wrote: > > Hi Florian, > > trying to get my head to understand the order of problems here: > Could you try to use a higher frequency (say, --freq 2e9 instead of > 3.5e6)? > I'd thing 3.51 MHz is out of range for the N310, anyway? > > Best regards, > Marcus > > On Wed, 2018-12-05 at 11:49 +0100, Florian Kaltenberger via USRP-users > wrote: >> So I can confirm that there is a frequency offset between the two >> USRP N310s when using only an octoclock (10MHz + PPS) to synchronize. >> I have measured with the tx_waveforms program >> ./tx_waveforms --args >> "addr=192.168.x.2,time_src=external,clock_src=external,master_clock_r >> ate=122.88e6" --rate 122.88e6 --freq 3.51e6 --wave-type SINE --wave- >> freq 10e6 --gain 100 >> on the first USRP N310 (x=10) and then on the other (x=20). There is >> an offset of 1200Hz between the peaks of the sinusoids between the >> two measurements. >> Using an external LO didn't change anything either. Unless I need to >> provide any other arguments in that case? >> I also tried to do a test where I use both USRPs simultaneously >> ./tx_waveforms --args >> "addr0=192.168.10.2,addr1=192.168.20.2,time_src=external,clock_src=ex >> ternal,master_clock_rate=122.88e6" --rate 122.88e6 --freq 3.51e6 -- >> wave-type SINE --wave-freq 10e6 --gain 100--channels "0,4" >> but unfortunately that does not work at all at my testbench (program >> hangs and no signal transmitted). >> My UHD version is 3.13.0.2 (UHD_3.13.0.HEAD-0-g0ddc19e5) >> Any help appreciated. >> Thanks! >> Florian. >> >>> On 04/12/2018 21:29, Florian Kaltenberger via USRP-users wrote: >>> Hi Marcus and Robin, >>> thanks for your answers, this is helpful information. I should add, >>> that I actually tried the synchronization with an octoclock (10MHz >>> + PPS), but it did not give me the expected results, i.e., I saw >>> some residual frequency offsets. But maybe I screwed up at some >>> point. Let me do some more measurements and get back to you on >>> this. >>> Florian. >>> >>>> On 04/12/2018 18:57, Marcus D. Leech via USRP-users wrote: >>>> On 12/04/2018 10:14 AM, Florian Kaltenberger via USRP-users >>>> wrote: >>>>> Hi there, >>>>> I just discovered that in addition to the external 10MHz >>>>> reference in, the USRP N310 also has external local oscilator >>>>> inputs, one for each daughterboard and each TX/RX. So does that >>>>> mean that in order to synchronize multiple N310 in frequency, >>>>> phase, and time, it is no longer sufficient to use an octoclock >>>>> to provide a 10MHz reference and PPS? If so, at what frequency >>>>> do you have to drive the external LOs and at what power? >>>>> Florian. >>>>> >>>> In addition to what Robin posted, I'll observe that the external >>>> LO port is an *additional feature* of this device. >>>> >>>> You should still be able to use the external 10MHz and 1PPS ports >>>> the same way you would with a B210 or E310, since the AD9371 >>>> front-end chip is similar to the AD9361 chip used in the B210 >>>> and E310. >>>> >>>> The thing about synchronizing multiple independent PLL >>>> synthesizers, though, compared to a strictly-shared-LO, is that >>>> the former will >>>> experience both phase ambiguities, and have a higher mutual >>>> phase-noise than the latter, which is why you might decide to >>>> choose >>>> the latter. >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> USRP-users mailing list >>>> USRP-users@lists.ettus.com >>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>> >>> -- >>> Follow us on Google+, LinkedIn, or Twitter! >>> >>> >>> _______________________________________________ >>> USRP-users mailing list >>> USRP-users@lists.ettus.com >>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >> -- >> Follow us on Google+, LinkedIn, or Twitter! >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >
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