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Re: [Discuss-gnuradio] USRP Basics questions

From: Somya Ajmera
Subject: Re: [Discuss-gnuradio] USRP Basics questions
Date: Tue, 14 Apr 2009 23:38:40 -0700 (PDT)

Hi Josh, on the  SMA connectors I had connected my transmit receive antennas. I wanted to know if while transmitting and receiving signals using USRP sink and source blocks, can I silmatenously probe any pin on the transmit/receive daughter board inorder to see the signal out and in to USRP. Also I was trying to make an OFDM system by implementing the following blocks:

Random Source:---->OFDM Modulator:------------>USRP Sink
[Minimum=0;                [ Modulation:8 QAM               [Unit Number=0
Maximum=2;                 FFT Length=512                   Interpolation=400
Num Samples=1M        Occupied tones: 200           Frequency=100M
Repeat=Yes]                 CP Length: 128                    Gain=0
                                      Pad for USRP=Yes              Side=Side A]
                                      Payload length=0]

After running this, when I probed pin tx0 - tx7 on the daughter board, I was able to see some waveforms on the scope. But when I build the receiver system:

USRP Source:----------->OFDM DeModulator:------------>FFT Sink
[Unit Number=0                [ Modulation:8 QAM              
Decimation=400                FFT Length=512                  
Frequency=100M              Occupied tones: 200         
Gain=0                                CP Length: 128                   
Side=Side A                                                  
RX Antenna=RXA ]                                   

I am get the following warning:
"** (python:4085): WARNING **: IPP request failed with status 1030
       Timeout "
and now if i probe the same pins on the daughter board, I am not able to see any waveforms. Can you please help me to figure out this behaviour.

Thanks & Rgards,
Somya Ajmera

--- On Tue, 14/4/09, Josh Blum <address@hidden> wrote:
From: Josh Blum <address@hidden>
Subject: Re: [Discuss-gnuradio] USRP Basics questions
To: address@hidden
Cc: "'address@hidden'" <address@hidden>
Date: Tuesday, 14 April, 2009, 9:57 AM

Somya Ajmera wrote:
> HI Josh, we have basic TX , RX daughter board with us. also what is that
range you have mentioned into your reply is for?

Many times, users give the usrp sink numbers between +/- 1.0 and there is no
transmit power. Just to double check, you should be giving usrp numbers around
+/- 10e3 :-)

As far as how you can see the signal:

You can hook up an oscilloscope to one of the SMA connectors on the basic TX
(TXA or TXB)

Or, connect the basic RX to the basic TX with SMA to SMA connector, and use a
program like usrp_oscope.py or usrp_fft.py to look at the received signal.


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