I'm so sorry, I'm new in this world and I'm still getting used to it.
I attach a GNU Radio screenshot where you can see the signal, it's an intermittent peak at 120,457 MHz (here it's my first question, as the signal is shifted in the FFT plot, why?). On that signal I want to set a power (in dB) threshold that I select manually its value, i.e: -50 dB.
Another question is if it's essential to filter the spectrum at the beginning to work only with the frequency where the highest peak takes place. Although I understand that in this case the threshold wouldn't be necessary, as I already have only the portion of spectrum to study, so this simplify too much the solution.
I'm actually interested in constantly saving the peak power value in dB of that signal, setting a manual threshold, and export all this information later on a file.
This is my last question, I've been reading information about "file sink function" but I can't understand how it works. Especially how I have to implement it to have in file the numerical values of power [i.e: -40,-41,-39, ...] and in which file format would be saved.