# How to measure signal power in GNU Radio.(I wondered how much dBm is specific.)

I used the "QT GUI frequency sink" and "WX GUI FFT sink" to measure the signal.

But I got different value. I would like to know what dB stands for in them. Whether it is dBm or just a ratio.

And yes, as you noticed, this is digital signal processing, so there's no physical units involved – the display axes are correctly labeled with "dB", as in "dB relative to an arbitrary reference vector", typically a energy=1 time signal (e.g. $(0,\ldots,0,1,0,\ldots,0)$), or a power=1 signal (e.g. $(1,\ldots,1)$).