[USRP-users] X310 + 2 CBX daughtercards strange behaviour

boeglen herve herve.boeglen at univ-poitiers.fr
Wed Sep 24 06:02:23 EDT 2014


Dear Ian, 

Thank you for your answer. Here is a pdf summarizing my
settings + tests. I also enclose my GRC flowgraph. 

As you can observe
from the graphs RF1 noise floor is 40dB higher that RF0. 

If persons
having the same board could tell me what I'm doing wrong for the
settings it would be great! I got no answer from Ettus' support...

Best regards 


On Tue, 23 Sep 2014 08:00:00 -0700, Ian Buckley

> Herve, 
> Your configuration is quite a common one (that
generally works well) so there's something more specific than just that
collection of hardware going on here. 
> I think at this point it would
be very helpful if you can attach your GRC flowgraph to a post and also
describe in some detail how you have cabled your X300 to the signal
source so that the chances of reproducing this independently are
> -Ian 
> On Sep 23, 2014, at 6:07 AM, boeglen herve via
USRP-users wrote: 
>> Hi all, 
>> I didn't get any answer to this
email so I send it again :-) 
>> Does anybody on the list use a X300
or X310 equipped with 2 radio boards and 10Gbit interface ? If so, have
they already tested a simultaneous TX or RX? 
>> This problem looks
to me as if the second daughter card is not configured properly. 
Thank you for your answers. 
>> Best regards 
>> Hervé 
-------- Original Message -------- 
>> Re: [USRP-users]
X310 + 2 CBX daughtercards strange behaviour
>> DATE:
>> Sat, 20 Sep
2014 09:35:19 +0200
>> FROM:
>> boeglen herve 
>> TO:
>> "Marcus
D. Leech" 
>> CC:
>> Mike Jameson , 
>> Hi, 
>> I know
pretty well the throughput limit of the 1Gbit interface, that's why I
use a 10 Gbit one :-) It's really impressive since it holds the 100Ms/s
using both channels. My machine runs a Core I7 2600k + 12 Gbyte RAM on
Ubuntu 14.04 64 bit (3.13 kernel, MTU set to 9000!). I use the latest
firmware with GNURadio 3.7.5. 
>> Concerning my problem, RF 0
channel (first CBX) has a noise floor around -100 dB on the spectum
scope whereas RF 1 (second CBX) goes up to -60 dB. However my settings
are the same for both channels. 
>> When mentioning the bandwidth,
It was to describe the behaviour of the signal on RF 1 (wider noise
>> Another noticeable difference between the two
channels is that you get a -55dB spike at 0Hz on RF 1. When performing
the Wifi test, everytime a packet enters, RF 1 channel's noise floor
increases around -60dB (over the 50MHz bandwidth). Really weird... 

>> Best regards 
>> Hervé 
>> On Fri, 19 Sep 2014 17:16:20
-0400, Marcus D. Leech wrote: 
>>>> Hi Markus and Mike, Thank you
for your answers. It does not change anything whether you specify the
subdev or not. Markus: yes everything is wired properly. Concerning the
last email, I used a BladeRF as a generator (0dBm + 30dB attenuator).
Here is another test with Wifi and as you can see from the two spectrum
scopes (upper is RF 1, lower RF 0), RF 1 reception bandwith seems to be
larger than for RF 0 (however it's set to 20MHz for both channels). I
have a second X310 with the same daugthercards and I get the same
behaviour... Is there a way to use just RF 1? I hope that going to sleep
is going to help me to find an idea to solve the problem :-) Best
regards Hervé
>>> The bandwidth setting doesn't do anything on the
CBX card--it's only 
>>> used to set the analog bandwidth between the
cards baseband/IF output, and
>>> the ADC.
>>> The bandwidth
delivered to the host depends, in this case, on the 
>>> specified
sample rate.
>>> What type of host interface are you using in this
case? From the 
>>> spectrum plots, it looks like you're asking for two
channels of 25Msps 
>>> each, which
>>> will not "fit" over 1GiGe at
16-bit samples.
>>> Do you get any 'O' being output while you run
this flow-graph? What 
>>> type of computer?
>> USRP-users mailing
>> USRP-users at lists.ettus.com [5]


[1] mailto:herve.boeglen at univ-poitiers.fr
mailto:mleech at ripnet.com
[3] mailto:mike.jameson at ettus.com
mailto:usrp-users at lists.ettus.com
mailto:USRP-users at lists.ettus.com
[6] mailto:usrp-users at lists.ettus.com
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