[Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back)

[Activecat]

Dear Sir,

I try to send square wave from one USRP to another.
The received signal at the receiver USRP is very different from what
was being sent.
This is just a very simple setup. What could be wrong ..?


Setup:
----------
There are two N210 USRPs with SBX daughtercards, connected
back-to-back using direct cable with a 30dB attenuator.

In the transmitter flow graph, there is one Signal Source feeding
complex signal to USRP Sink.
In the receiver flow graph, there is one USRP Source feeding complex
signal to WX GUI Scope Sink.

The pictures of WX GUI Scope Sink are attached.


Blocks setting:
---------------------
Signal Source Block in the transmitter flow graph:
 Sample Rate: 32k
 Waveform: Square
 Frequency: 100
 Amplitude: 1
 Offset: 0

USRP Sink in the transmitter flow graph:
 Samp Rate(Sps): 32k
 Ch0: center Freq(Hz): 400.0045e6  (after calibration)
 Ch0: Gain (dB): 0

USRP Source in the receiver flow graph:
 Samp Rate (Sps): 32k
 Ch0: Center Freq (Hz): 400M
 Ch0: Gain (dB): 0



Software version:
-------------------------
Transmitter PC runs gnuradio 3.7.2.1 on debian 7.4 (32bit) using Dell PC.
Receiver PC runs gnuradio 3.7.2.1 on Ubuntu 13.10 (64bit) using iMac hardware.

Please advise, thank you very much.

Regards,
Activecat
Email: address@hidden

1-transmit.png
Description: PNG image

2-received.png
Description: PNG image