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

Marcus D. Leech mleech at ripnet.com
Tue Sep 23 10:16:45 EDT 2014

On 09/23/2014 09:07 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
I just did a quick test with an X310, with a WBX and a CBX (that's all I 
have), across 1GiGe, at 5Msps per side, driving an FFT sink in Gnu Radio.

Using UHD:

linux; GNU C++ version 4.7.2 20121109 (Red Hat 4.7.2-8); Boost_105000; 

And matching firmware/FPGA on the X310.

The result was two very-similar FFT plots at 1300MHz, 20dB gain, with 
only about 1dB difference in the noise-floor and DC-anomaly levels.

> -------- Original Message --------
> Subject: 	Re: [USRP-users] X310 + 2 CBX daughtercards strange behaviour
> Date: 	Sat, 20 Sep 2014 09:35:19 +0200
> From: 	boeglen herve <herve.boeglen at univ-poitiers.fr>
> To: 	"Marcus D. Leech" <mleech at ripnet.com>
> Cc: 	Mike Jameson <mike.jameson at ettus.com>, <usrp-users at lists.ettus.com>
> 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 bandwidth).
> 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?
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Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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