# D(overflow) when USRP2 as Rx and S(Packet drop?) as Tx

**URL:** <https://www.ruby-forum.com/t/d-overflow-when-usrp2-as-rx-and-s-packet-drop-as-tx/240987>\
**Category:** GNU Radio\
**Created:** [May 8, 2014, 4:20pm UTC](https://www.ruby-forum.com/t/d-overflow-when-usrp2-as-rx-and-s-packet-drop-as-tx/240987 "2014-05-08T16:20:18Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [May 8, 2014, 4:20pm UTC](https://www.ruby-forum.com/t/d-overflow-when-usrp2-as-rx-and-s-packet-drop-as-tx/240987/1 "2014-05-08T16:20:18Z")

</div>

hi,  
Im using a USRP2 as 2 Rx(Antenne J1 and J2).and using a USRPN210 as Tx.  
when I started flow graph, i saw ‘DDDDDDD’ keeping showing up.and when I  
changed USRP2 as 2 Tx and USRPN210 as Rx, i saw ‘SSSSSS’.

I also tried turn the realtime scheduling on.But it killed the flow  
graph immediatly after i started my flow graph.

above is the setting im using:  
samp\_rate=2M  
carrier\_freq=2.49G

problem may come from the USRP2.thats also what i wonder after checking  
[http://www.ettus.com/content/files/kb/application\_note\_frontends\_subdevices\_antenna\_ports.pdf](http://www.ettus.com/content/files/kb/application_note_frontends_subdevices_antenna_ports.pdf)

it says USRP2 can be used as 2 Rx at sametime or 1 Rx and 1Tx.  
so i even tried use USRP2 as 1Tx sending pure cos signal but in the Tx  
side i saw nothing showing up.

is there something i made wrong or it just the time i sould upgrade my  
computer?(which the most googled solution of the problem)

Yao