Re: [Discuss-gnuradio] question regarding usrp_fft.py

[adib_sairi]

thank you firas for the explanation..


Firas A. wrote:
> 
> 
> So, what is the factors that effect dB conversion?. The first value is the
> FFT size, so that when we change the FFT size, the formula should
> compensate for this. Second we should compensate for the taps of the
> window used for FFT (Hanning, Hamming,...etc).  
> 
> 

is the fft_size effect the value of db? for plotting the GUI (the display of
the spectrum analyzer) in fftsink_nongl.py, inside the set_data function, we
can see that each of the bin of the fft is treated as individual i.e
evt.data[0], evt.data[1], evt.data[2], and so on. this data is use to plot
the graph inside the GUI of the spectrum analyzer. so if the bin of fft is
treated as individual, what is the relationship between fft_size and the db
calculation? what is the usage of fft_size in the calculation?

if i choose to monitor the 2.5G center frequency, so the evt.data[0] is the
place where the 2.5G is right? if the fusb is 4Ms/s and our fft bin is 256,
so our bandwidth of monitoring is only 2MHz right? and evt.data[1] to
evt.data[128] is the positive side of my signal while evt.data[129] to
evt.data[256] is my negative side.. am i right?



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