[Discuss-gnuradio] Problems with fft_sink_f

[Erlend Barstad Strand]

Hi

I am quite fresh on GNU Radio so please exscuse me if ask stupid
questions.

I simlpy want to view the fft of two sines.
Code:
"
self.src0 = gr.sig_source_f (sampling_freq, gr.GR_SIN_WAVE, 350, ampl)
self.src1 = gr.sig_source_f (sampling_freq, gr.GR_SIN_WAVE, 440, ampl)

self.src = gr.add_ff ()

self.connect(self.src0, (self.src, 0))
self.connect(self.src1, (self.src, 1))

self.scope = fftsink.fft_sink_f (self, panel, 512,
       sampling_freq, fft_rate = 1)

self.connect (self.src, self.scope)
vbox.Add (self.scope.win, 1, wx.EXPAND)
"

when the window opens there seems to be a sensible spectrum for a very
short period of time, then it flats out and doesnt make much sense.

I have tried changing the fft_rate, sampling_freq and various other
parameters, but the same problem occurs. I have also tried using
fftsink.make_fft_sink_f, but also then a similar problem occurs. After
a very short time the blue line drawing the spectrum disappears.


--
Erlend Barstad Strand