Re: [Discuss-gnuradio] Issues transmitting and receiving simultaneously on B210

[Marcus D. Leech]

On 07/20/2017 02:23 AM, Jose Ruvalcaba wrote:

Hello,

I'm currently having issues simultaneously transmitting and receiving data from one B210 to another B210. My goal is to send Tx data from one B210 and have it be received and re transmitted from a second B210 back to the first. I am trying to use both channels (RF A and RF B) to simultaneously transmit and receive on both radios. To do this I have set the "Mb0 Subdev Spec" to "A:A A:B" on both the USRP source and sink blocks, as I have shown in the flowgraphs attached. My radio can successfully transmit data from one B210 and have it be received in the second B210. However, my issue arises when my second B210 tries to re transmit the received data back to the original B210 (This is shown if usrp_2_channel.png flowgraph). 

My question is, in order to accomplish successful Tx to Rx loopback on both radios, do I need to label the Subdev spec section as A:A A:B? Have I labeled the Subdev correctly for a B210 or do I need to change it? Is it possible for a USRP to transmit and receive simultaneously on both RFA and RFB channels of a B210? If so, can I do this while using different frequencies on each channel?  Just for completeness I have both radios connected to each other using coaxial cables with a 38dB attenuation between each path.  

Thanks,

Jose

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Jose:

Your basic problem is that on the B210, the synthesizer for BOTH TX channels is shared, and the synthesizer for both RX channels is shared.

This means that ordinarily both channels have to be tuned to the same frequency.   There are ways to "cheat" if your two desired "air" frequencies
  are close together, but in your case, they are 30MHz apart.