Same procedure I outlined before. You need to feed a CW tone (via cable)
directly into the USRP and spectrum analyzer, compare spectrum amplitudes,
and multiply the USRP samples by 10**(offset_dB/20.0). Noise or a modulated
signal makes things more difficult since spectrum analyzer must be put
I transmitted this -30 dB signal (Image 1) using a usrp: The spectrum
analyzer displays -50 dBm (Image 2) as its reading. My receiver end picked
up the signal with the same peak power at -30 dB (Image 3). I'm confused.
How do I convert the dB power in the GRC to the received signal of the
I misread you question and thought you were receiving with the USRP. Same
procedure, just don't let the transmitted signal go past +/- 1.0 or you will
clip the DAC. In practice keep it backed off 6 dB or more to allow for
crest factor.
Lou
madengr wrote
1) Send in a CW tone from a signal
1) Send in a CW tone from a signal generator of known power (dBm)
2) Read the level from GR FFT (dB)
3) Figure out the amount you need to offset (dB)
4) Multiply your samples by a constant value of 10**(offset_dB/20.0)
5) The GR FFT will now be calibrated to an absolute power (dBm).
Note if you
