Re: [Discuss-gnuradio] Spectrum Analysis with FFT plotting

[Sebastiaan Heunis]

Ujala

You have to use usrp.tune(self.u, 0, self.subdev,106.2e6).  This will
mix whatever is at 106.2MHz down to DC.  set_rx_freq is used to
control the DDC in the USRP and only works from -32e6 to 32e6MHz.

The tune function first uses the mixer in the TVRX db to mix the
signal down to 5.75MHz (the TVRX db that I'm using mixes the signal
down to 44MHz).  If you're using your db, the signal gets sampled and
sits at 5.75MHz.  The DDC now needs to mix it down to DC.  The tune
function takes care of both of these functions for you.

Try to capture a signal by setting decimation to 250 and tuning to
106.2MHz.  The result should be a signal shaped like a bell that
nearly spans the entire length of the plot.

Sebastiaan