Re: [Discuss-gnuradio] [USRP-users] Spectrum analyzer not picking up any signal from USRP-GNU Radio

[Derek Kozel]

Hello Ayaz,

UHD will log to standard out by default. You should be seeing it in the console section of the GNU Radio Companion, at the bottom.

Multiplying by 500 will almost certainly lead to the signal clipping at the DAC, completely corrupting your signal. The USRP Sink block expects values between -1.0 and 1.0. The sample rate of 32kHz is very low. It should work, but the general guidance is to use a somewhat higher rate as this helps lessen the impact of the FPGA's filters on your passband signal.

Have you observed any signal from the USRP on your spectrum analyzer? Starting with uhd_siggen_gui and making sure your spectrum analyzer is setup correctly may be the best place to start, then your own GNU Radio flowgraph with just the signal source going into the USRP Sink, then add the OFDM modulation once all the rest is working.

Regards,

Derek

On Mon, Jun 11, 2018 at 9:47 PM, Ayaz Mahmud <address@hidden> wrote:

Hi Derek,

 

Thanks for pointing, I initially thought as the throttle was connected to WX GUI FFT it won’t affect the USRP sink.

 

But the issue does not get resolves even after the throttle is removed. I tried increasing the gain to 30 and adding a multiply constant of 500 after the OFDM Mod block.

 

As a beginner I did not knew about the log file. As I check the documentation the file is /usr/include/uhd/utils/log.hpp but I am not sure how to run/see this logging. Any document link that you can provide as an example?

 

On another hand I have tried implementing the exact same flow as in the link https://wiki.gnuradio.org/index.php/Guided_Tutorial_Hardware_Considerations - “The PSK Mod with USRP sink” one. And I am unable to get any output in spectrum analyzer as shown.

 

Thanks,

Ayaz

 

From: Derek Kozel <address@hidden>
Sent: Monday, June 11, 2018 1:34:01 PM
To: Ayaz Mahmud
Cc: address@hidden
Subject: Re: [USRP-users] Spectrum analyzer not picking up any signal from USRP-GNU Radio

 

Hello Ayaz,

Because you have hardware in your flowgraph (the B210) you should not include a throttle block. Check your log output, it is very likely that UHD is reporting underflows.

I'd recommend quickly running through the GNU Radio tutorial on using hardware.
https://wiki.gnuradio.org/index.php/Guided_Tutorial_Hardware_Considerations

Also the UHD manual has some general guidance which will help you to understand UHD's messages.
http://files.ettus.com/manual/page_general.html

Regards,

Derek

 

On Mon, Jun 11, 2018 at 8:26 PM, Ayaz Mahmud via USRP-users <address@hidden> wrote:

Hi,

 

GNU Radio version 3.7.11

USRP B210 with 1 x 2.4GHz antenna

Spectrum Analyzer with 2.4 GHz antenna

I am trying to transmit the below flowgraph through USRP and receive a signal with Spectrum Analyzer. Though the Spectrum analyzer will not be able to demodulate it should show a stable frequency. Unfortunately, the spectrum analyzer does not pick any signal while calibrated at Center Freq: 2.412 GHz.

GNU-Radio console warning:

gr::log :WARN: ofdm_mapper_bcv0 - The gr::digital::ofdm_mapper_bcv block has been deprecated.

gr::log :WARN: ofdm_insert_preamble0 - The gr::digital::ofdm_insert_preamble block has been deprecated.

 

GNU Radio version 3.7.11

USRP B210 with 1 x 2.4GHz antenna

Spectrum Analyzer with 2.4 GHz antenna

Block diagram attached.

I am trying to transmit the below flowgraph through USRP and receive a signal with Spectrum Analyzer. Though the Spectrum analyzer will not be able to demodulate it should show a stable frequency. Unfortunately, the spectrum analyzer does not pick any signal while calibrated at Center Freq: 2.412 GHz.

GNU-Radio console warning:

gr::log :WARN: ofdm_mapper_bcv0 - The gr::digital::ofdm_mapper_bcv block has been deprecated.

gr::log :WARN: ofdm_insert_preamble0 - The gr::digital::ofdm_insert_preamble block has been deprecated.

 

Where can this possibly go wrong?

 

 

 

Thanks,

Ayaz

 

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