[USRP-users] USRP X310 motherboard issues

Marcus Müller marcus.mueller at ettus.com
Wed Dec 10 14:30:12 EST 2014


Hello Tim,

this is in fact quite a bit surprising. I have no idea where the 500kHz
spaced tones in your QPSK_B.png came from, so I'm really just guessing
around how to narrow down reasons:

The numeric values seem to be low, but I want to be on the safe side:
* How much input power are you providing (please make sure to stay below
-15dBm!)?
* If you reduce input power/voltage, does the effect decrease?
* Does it get worse when you increase the analog gain?
* could you please tune to let's say 303.25MHz?
* If you run the osmocom Spectrum Browser with
-a "lo_offset=15000000"
does the picture change dramatically?

This is all very generic... I can't really explain the little spikes in
your multi_tone_B.png, so far.
Between the daughterboard and the ADC is only a (if I remember
correctly) 6GHz RC lowpass; so no active active parts that would explain
these spikes.#

I hope this can be solved fast!

Best regards,
Marcus Müller


On 12/10/2014 07:02 PM, Timothy Schaffer via USRP-users wrote:
> I received an X310 from NI last week along with 2 x WBX-120 boards and I've
> noticed a difference in signal quality between the A and B subdevs of the
> motherboard. Overall, It seems the signals receive from the B side are
> generally distorted and prone to harmonics. I naturally assumed this was an
> issue with the WBX boards, so I swapped them and noticed the same issues.
> Next I swapped the cables connected to the bulkhead and still the same
> issue.
> I''m currently using UHD 3.008.000-52, but have not tried other versions.
> I've reloaded the FPGA firmware, ran all 3 cal routines on both subdevs.
> I'm not sure what else to try? I'v eattached a couple of screen shots of
> some of the tests I performed with an HP E4432B. The tests were done back
> to back using the same cable from the siggen to the USRP.
>
> You can see in these two screen shots, the actual distortion to the
> waveform in the scope.
> [image: Inline image 2].[image: Inline image 1]
>
> Here is a DQPSK(24.3ksps) test signal at 303 MHz
>
> [image: Inline image 3][image: Inline image 4]
>
> Any ideas on what could be wrong, or does it need to go back to NI for
> repair/replace?
>
> -Tim
>
>
>
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> USRP-users at lists.ettus.com
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