Connecting a CDA-2990 to Multiple USRP-2945s

Updated May 14, 2018

Reported In


  • USRP-2945
  • CDA-2990

Issue Details

I have a CDA-2990 and two USRP-2945s. I would like to synchronize my application so I can receive on all eight channels across both of my USRPs. How do I connect the CDA-2990 to the USRPs, and how can I share the local oscillator (LO) between each USRP?


The CDA-2990 provides eight 10MHz clock outputs. Connect one of these 10MHz outputs to the REF IN connector on the back of each USRP you are using. This ensures that all USRPs are looking at the same clock source, and it allows synchronization of the USRPs.

Each USRP-2945 also has two LO OUT connectors (IF 1 and IF 2). These should be connected to the corresponding LO IN connectors on the second USRP. If additional USRPs are being used, this connection can be daisy-chained. For example. connect LO OUT of the first USRP to LO IN of the second USRP. Then connect LO OUT of the second USRP to LO IN of the third USRP, and so on. 

Additional Information

For additional information on LO sharing and synchronization with the USRP-2945 and USRP-2955, please refer to the Introduction to the USRP-2945 and USRP-2955 Software Defined Radios LO Sharing and Synchronization section


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