Re: [Discuss-gnuradio] Gnuradio FFT - Graph concatenation

[Tom Rondeau]

On Thu, Jun 11, 2015 at 10:25 AM, Hassaan Ahmad <address@hidden> wrote:

Thanks for the guidance.

Can I do this message passing in GRC? Also, how would the bandwidths get concatenated together and displayed in the same FFT graph?

Check out our tutorials on gnuradio.org for message passing help. In the FFT blocks, go into the Properties and in the General tab at the bottom there's a "Show Msg Ports" option that you'll need to turn on.

You wouldn't be able to concatenate the signals in the plot. The plots are designed for real-time use, so each time plots, it's based on the newest signal information in the data stream. So the old stuff would be gone. The message port just changes the center frequency with the same bandwidth.

What you want is very specialized, so you'll probably have to write something of your own for this.

Tom

 

On Jun 11, 2015 7:08 PM, "Tom Rondeau" <address@hidden> wrote:

On Thu, Jun 11, 2015 at 9:59 AM, Hassaan Ahmad <address@hidden> wrote:

Hi,

I'm using USRP E310 and running uhd_fft.grc to acquire FFT spectrum from the device in network mode, and then displays that with QT FFT GUI block. 

Setting a center frequency, I can get an instantaneous bandwidth of 32MHz around the center frequency. (for me it's the maximum in network mode) Now, I want to change the center frequency programmatically in order to sweep a larger bandwidth and then concatenate the results into a single QT FFT graph like this: 

-IQ/2-----Cent.freq1-----+IQ/2    -IQ/2-----Cent.freq2------+IQ/2    -IQ/2-----Cent.freq2------+IQ/2  ...

Is their a way I can do it?

Regards,

The QTGUI FFT sink has a message port that allows you to control the center frequency. See the Detailed Description here

http://gnuradio.org/doc/doxygen/classgr_1_1qtgui_1_1freq__sink__c.html

Tom