Re: [Discuss-gnuradio] FFT plot unit

[Sylvain Munaut]

Hi,

> I was able to gather results, and I am really confused with it. I generated
> a -30 dB signal based on the fft plot shown and transmitted it using a usrp.
> My spectrum analyzer received a signal at -50 dBm (-80 dB) and my receiver
> which also uses a usrp received the signal and plotted it at -30 dB. My
> question is, what is the unit of the fft plot? Is it dB or dBm?

They're dBFS  or dB Full Scale ...

So they're just relative to the "full scale" range defined in GR as -1.0 ... 1.0

USRP are not calibrated instruments, so you can't map this to dBm or
any absolute power measurement. Only relative measurements are valid.



Cheers,

   Sylvain