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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: <br>
The numeric values seem to be low, but I want to be on the safe
* How much input power are you providing (please make sure to stay
* If you reduce input power/voltage, does the effect decrease?<br>
* Does it get worse when you increase the analog gain?<br>
* could you please tune to let's say 303.25MHz?<br>
* If you run the osmocom Spectrum Browser with<br>
does the picture change dramatically?<br>
This is all very generic... I can't really explain the little spikes
in your multi_tone_B.png, so far.<br>
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.#<br>
I hope this can be solved fast!<br>
<div class="moz-cite-prefix">On 12/10/2014 07:02 PM, Timothy
Schaffer via USRP-users wrote:<br>
<pre wrap="">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
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
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