R&D did some testing and indeed at least in UHD 4.0 the spectrum is inverted.
Hopefully a fix will be available soon now that it is confirmed. Sent from my iPhone > On Nov 3, 2020, at 3:27 PM, Marcus D. Leech <patchvonbr...@gmail.com> wrote: > > On 11/03/2020 02:54 PM, Jason Roehm via USRP-users wrote: >> >>> On 10/14/20 2:41 PM, Marcus D. Leech via USRP-users wrote: >>> On 10/14/2020 01:28 PM, Jason Roehm via USRP-users wrote: >>>> I have an N320 that I'm trying out for the first time. I'm using UHD >>>> 4.0.0, and I loaded the corresponding root filesystem data for that >>>> release to the N320. I find that when the receiver is tuned to frequencies >>>> below 450 MHz, the spectrum is inverted. When you tune to 450 MHz or >>>> above, the spectrum is upright as expected. See the attached screenshots >>>> for example spectral plots. >>>> >>>> There are several ATSC signals visible in the spectrum. I simply used an >>>> indoor antenna, so there is a lot of multipath on the signals causing >>>> their spectra to be very non-flat, but the telltale sign of spectral >>>> inversion here is where the pilot tone is appearing on each one. In the >>>> first plot, tuned to 440 MHz, they appear on the right of each signal; >>>> this is not where they should be. When you tune to 450 MHz, the location >>>> of the signals flip to the right half of the plot, and the pilot tone is >>>> on the left, where they belong. >>>> >>>> Is this a known issue? >>>> >>>> Thank you. >>>> >>>> Jason >>> I'm discussing this with R&D right now. It's *conceivable*, because >>> there's an extra mixer stage in the below-450-mhz pathway, and that >>> mixer stage uses "high side" LO injection, which would produce an inverted >>> spectrum, but the FPGA would "know" this and invert it back... >>> >> Marcus, >> >> Did you ever get any resolution on this issue? >> >> Jason >> >> > I've raised the issue with R&D, but not heard back. I'm hampered by not > having an N320 in my own lab to test this. > > Presumably, the issue you see is version independent? > > > _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
