Could you confirm that you’re using at least 30dB of attenuation in the coax link?
Sent from my iPhone > On Mar 25, 2021, at 6:27 PM, Jerrid Plymale <jerrid.plym...@canyon-us.com> > wrote: > > > Yes, moving TX out of the RX band has no affect on the noise level increase. > > Best Regards, > > Jerrid > > From: Marcus D Leech <patchvonbr...@gmail.com> > Sent: Thursday, March 25, 2021 2:29 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 > > If you move the TX out of band with respect to the RX do you still see the > noise when the TX graph starts? > > > > Sent from my iPhone > > > On Mar 25, 2021, at 3:57 PM, Jerrid Plymale <jerrid.plym...@canyon-us.com> > wrote: > > > So I was able to test setting up both USRPs with the same 10 MHz reference > signal, and there was no improvement to the noise being added. > > If the flowgraph just emits a CW tone, we see a similar response, the added > noise is still there and at the same level, we just have the added spike of > the CW tone at the frequency we set it to. > > Best Regards, > > Jerrid > > From: Marcus D Leech <patchvonbr...@gmail.com> > Sent: Wednesday, March 24, 2021 5:01 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 > > 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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