Real time FFT resolution

[Frank_V2]

Good day to every body 

I'm playing with an ETTUS B200 mini for doppler frequency monitoring.

To analyze the spectrum in real time, I'm currently using uhd_fft.py (gnuradio application). The problem is that the maximum fft sample number is 4096, while I need 2^14 samples. 

I tried to investigate into the c++ files (invoked by uhd_fft.py), such as freq_sink_c_impl.cc (https://github.com/gnuradio/gnuradio/blob/master/gr-qtgui/lib/freq_sink_c_impl.cc) whose line 216 describes the following action:
216 throw std::runtime_error("freq_sink: FFT size must be > 16 and < 16384.");

The problem seems to be hard without the whole file list to be recompiled....

Would anybody help me ?

Thank you very much!!

Grazie,

ciao

[AndresA]

Hi Frank,

I recommend you as you propose to recompile all the files..otherwise is hard to understand the behavior of the code used...

Then, try to increase the fft sample number...

BR,

Andres

[AndresA]

Hi Franks,

Did you try to recompile all the files?

Andres

[Frank_V2]

Hi Andres, thank you for your response. I have been on business trip and I could see your message just now. Honestly speaking I'm not sure which files should be recompiled. There are many dependencies and it looks like a juniper bush -:)

Do you have already experienced the same problem?

Further, before recompile I guess I should modify the part of codes (in one or more file, cc and h) where the limit to 2^12 is set. What do you think about ?

Thank you again for your help

Have a nice day  

[AndresA]

Hi Frank,

Unfortunately I do not have experience with this kind of problem 😞 

But I think is very interesting.

Try to recompile the file and then see what happens.

Have a great day!