Re: FFT in Octave

[Mike Miller]

On Sat, Jul 20, 2013 at 13:41:16 +0100, DECROP Fabrice wrote:
> I'm Fabrice, amateur radio with F4BJH callsign, and let me tell you I've
> porblems with FTT implementation under Octave.
>
> I'm trying to simulate a CW carrier, and waiting for a 144,425MHz carrier,
> but I don't see that. CW message is only "1", meaning that there is only
> carrier at this frequency. I don't understand why I don't get this.
>
> Someone could tell me what wrong witch my code ?

Hi, can you explain what you think is not working and what you
expected to get more clearly?

I looked through your code briefly and the screenshot and it looks to
me like you are getting the CW signal you intended to generate. I see
that you set your sample rate to 10x the carrier RF, and it's clear
from the screenshot that there is a carrier at 70, which is 1/10 of
700, the size of the frequency-domain vector you are plotting. You
could plot it against a frequency vector of real units to get
something more legible:

  f = linspace (0, 10*f_F5ZAM, numel(dsp_rf_out));
  plot (f, 20*log10 (dsp_rf_out))

Does that address what wasn't working for you?

-- 
mike