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

boeglen herve herve.boeglen at univ-poitiers.fr
Tue Sep 23 09:07:13 EDT 2014


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 


-------- Original Message --------

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

 		Sat, 20 Sep 2014 09:35:19 +0200


		boeglen herve 

 		"Marcus D. Leech" 

 		Mike Jameson ,


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 


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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