You don’t need 1PPS for this. Having an external high quality reference may help, assuming my guess about your issue is correct.
What happens if your flow graph just simply emits a Cw tone, using the mute function perhaps tied to a GUI control or some such. Sent from my iPhone > On Mar 24, 2021, at 7:13 PM, Jerrid Plymale <jerrid.plym...@canyon-us.com> > wrote: > > > Ok, if that’s the case, would it help to have both USRPs connected to the > same 10 MHz reference signal and PPS? In this situation, would I need to > provide a secondary source for the PPS, or can that use the 10 Mhz reference > as well? > > Best Regards, > > Jerrid > > From: Marcus D. Leech <patchvonbr...@gmail.com> > Sent: Wednesday, March 24, 2021 2:23 PM > To: Jerrid Plymale <jerrid.plym...@canyon-us.com> > Cc: USRP-users@lists.ettus.com > Subject: Re: [USRP-users] Strong noise added to signal transmitted by X310 > with a UBX 40 daughterboard > > On 03/24/2021 05:10 PM, Jerrid Plymale wrote: > The devices are operating using direct connection via coax cables. > You absolutely need to put a 30dB attenuator in-line to prevent RX > destruction in the case of "ooops" moments from setting the TX > power output too high. > > > > The target frequency is 1.57542 GHz, and our current bandwidth is 4 MHz. We > will need to increase the bandwidth to 20 MHz soon for further system > development. > > The TX and RX gain are maxed on the receiving hardware. The TX gain of the > transmitting hardware is set to 0, as at max the noise strength increases to > ~ 20 dB. > > Attached are images of the FFT provided by the Frequency Sink in Gnuradio. > Hopefully these give a visual aid for the problem at hand. When I have the > transmitter USRP turned off (image 1), it would seem like the noise floor > coming into the USRP is around -94 dB. When the transmitter is turned on and > the flowgraph is started with the transmitted signal muted (I am using a > python block with code to create custom signals that is then connected to a > mute block that then connects to the UHD USRP sink block to be able to mute > the signal during runtime), the noise floor increases to around -78 dB. > > Best Regards, > > Jerrid > You are likely just seeing the LO leakage, along with the inevitable > phase-noise curve of the LO. > > > > > From: Marcus D Leech <patchvonbr...@gmail.com> > Sent: Wednesday, March 24, 2021 11:58 AM > To: Jerrid Plymale <jerrid.plym...@canyon-us.com> > Cc: USRP-users@lists.ettus.com > Subject: Re: [USRP-users] Strong noise added to signal transmitted by X310 > with a UBX 40 daughterboard > > Is the j B is over-the-air or direct connection? > > What frequency? Bandwidth? > > Do you have TX and RX gain turned all the way up? > > Can you share your flow-graphs, or minimum > Graphs that show the problem? > > Sent from my iPhone > > > > On Mar 24, 2021, at 12:20 PM, Jerrid Plymale <jerrid.plym...@canyon-us.com> > wrote: > > > Hello All, > > I have been running tests in which I am transmitting a signal from one USRP > X310 that’s using a UBX 40 daughterboard, and that signal is being received > by another USRP X310 using a UBX 40 daughterboard. I have noticed that when I > have the receiving USRP running with the Gnuradio flowgraph active, as soon > as I start the transmitting USRP’s Gnuradio flowgraph, there is a jump in the > noise floor as it is seen by the receiving USRP, and its roughly a 14 dB > increase. This occurs even if I have the signal being transmitted muted. Does > anyone have any idea what the source of this added noise could be? It is > something that I need to mitigate as much as possible for the tests I am > running using these USRPs. Any feedback will be greatly appreciated, thanks! > > Best Regards, > > Jerrid > _______________________________________________ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-le...@lists.ettus.com >
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