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

Marcus D. Leech mleech at ripnet.com
Wed Sep 24 08:31:38 EDT 2014

On 09/24/2014 06:02 AM, boeglen herve via USRP-users wrote:
> 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
> Hervé
Actually, Herve, I've been replying to you on the mailing list--I'm one 
of three people behind support at ettus.com.

Be that as it may, we'd still love to see a diagram showing how your 
signal sources are connected (physically) to the X310.  Also, does this
   problem follow the CBX card?  That is, if you swap CBX cards, does 
the "bad" channel follow the CBX card?

> On Tue, 23 Sep 2014 08:00:00 -0700, Ian Buckley wrote:
>> 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 maximized.
>> -Ian
>> On Sep 23, 2014, at 6:07 AM, boeglen herve via USRP-users 
>> <usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>> 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 --------
>>> 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 
>>> <mailto:herve.boeglen at univ-poitiers.fr>>
>>> To: 	"Marcus D. Leech" <mleech at ripnet.com <mailto:mleech at ripnet.com>>
>>> Cc: 	Mike Jameson <mike.jameson at ettus.com 
>>> <mailto:mike.jameson at ettus.com>>, <usrp-users at lists.ettus.com 
>>> <mailto: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?
>>> _______________________________________________
>>> USRP-users mailing list
>>> USRP-users at lists.ettus.com <mailto:USRP-users at lists.ettus.com>
>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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