# Benchmark\_rx.py problem

**URL:** <https://www.ruby-forum.com/t/benchmark-rx-py-problem/232177>\
**Category:** GNU Radio\
**Created:** [September 23, 2014, 11:01am UTC](https://www.ruby-forum.com/t/benchmark-rx-py-problem/232177 "2014-09-23T11:01:10Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [September 23, 2014, 11:01am UTC](https://www.ruby-forum.com/t/benchmark-rx-py-problem/232177/1 "2014-09-23T11:01:10Z")

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Hello,  
I’m trying to find packet loss in a real communication. I’m working with  
USRP N210, and I’d like to transmit and receive with benchmark\_tx.py and  
benchmark\_rx.py in OFDM mod.

At the transmitter, using  
./benchmark\_tx.py -f 2.45G -a “addr=192.168.10.2” -m qpsk  
all is OK, because I see the correct FFT at the receiver (using  
uhd\_fft.py).

When I try to receive using  
./benchmark\_rx.py -f 2.45G -a “addr=192.168.10.2” -m qpsk  
I don’t see the receiver packets or anything else. Sometimes the  
terminal returns TIMEOUT.

Could anybody help me?

Thanks a lot!

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<div class="post-metadata">

**Author:** ![mett\_bon](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/b2d939/32.png) [@mett\_bon](https://www.ruby-forum.com/u/mett_bon)\
**Post date:** [September 24, 2014, 3:19pm UTC](https://www.ruby-forum.com/t/benchmark-rx-py-problem/232177/2 "2014-09-24T15:19:30Z")

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Hello Mattia,

First thing you need to make sure of is whether a LO offset between Tx  
and Rx exists. If so, you need to compensate for it.

You’d also better change the gains for both transmitter and the receiver  
until you get the link work.

Regards,  
Zaher