The device manual is probably the best place to start reading (
https://files.ettus.com/manual/page_usrp_x4xx.html). As for your example,
streaming 2 Gsps through GNU Radio (or any other software) is tricky. I
would expect your session to cough up a lot of errors/warnings about being
unable to keep up (like, UUUUUUUUU.... or OOOOOOOOO...).

The RF settings also don't match up. Your MCR is 2 Gsps, which will let the
converters run at 4 GHz (
https://kb.ettus.com/About_Sampling_Rates_and_Master_Clock_Rates_for_the_USRP_X440#X440_Supported_Master_Clock_Rates_.28MCR.29).
So your first Nyquist zone is < 2 GHz. But both your center frequency and
sine wave frequency are at 1 GHz, so you've moved your signal out of that
zone.

I would suggest starting with much, much lower rates until you see the
signal that you expect (start with 125 Msps). You can scale up rates as you
go. If you're in the few-hundred-megasamples range, your computer should be
able to keep up.

Best of luck,

---M

On Fri, Sep 26, 2025 at 9:39 AM Peter Gu via USRP-users <
[email protected]> wrote:

> I was able to set the MCR via device args in RFNoC Graph. I got it from an
> example…however i found nothing in the documentation
> <https://wiki.gnuradio.org/index.php?title=RFNoC_Graph_(Device)> about
> that. Am I looking into the wrong specs or is the idea to look into the c
> code?
>
>
> Moreover, with Ch0 bandwidth also set to 1.6GHz now, I still cannot detect
> the cosine signal in loopback mode…did i still miss something?
>
> Best,
>
> Peter
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