Re: [Discuss-gnuradio] Visualizing Amplitude spectrum instead of power spectrum

[Federico 'Larroca' La Rocca]

Sorry, the last mail was sent by who-knows-what-shortcut...

So, if what you want is to visualize the complex vector resulting from the DFT, you should use the FFT block, followed by a vector to stream and then a QT Time Sink with number of points as many as in the FFT windows size. This will show you the real and complex part (pay attention to the shift parameter in the FFT). That is very similar to what Marcus wrote before (I've never used QT Vector Sink, and use stream to vector and a matching qt time sink instead).

If you want either the magnitude or the phase, there are a couple of blocks that do just (complex to mag, complex to arg, complex to mag and phase) and may be used with vectors, again as Marcus said.

best

Federico

2017-04-26 17:07 GMT-03:00 Federico 'Larroca' La Rocca <address@hidden>:

Hi,

If what you want is to visualize the complex resulting from the DFT, you should use the FFT block, and then a QT

2017-04-26 15:33 GMT-03:00 Fernando <address@hidden>:

El 26/04/17 a las 20:01, Marcus Müller escribió:

I call it simply spectrum too, maybe I should have said magnitude/phase spectrum.

Now I'm confused. Magnitude spectrum is definitely my ; but you're just looking for a plot of the DFT, right?

Yes, but not only magnitude(DFT) but also phase(DFT)

So I'd like to get back to my earlier question:

What is the purpose of this?

I was doing TX+RX of a FM stereo signal and something did not work. I was searching for the error and I found the error was in the modulation or demodulation, but I could not see where.
This diagram was working faulty, and I thought that maybe I was messing up with signs when doing add/substract, so I wanted to see the spectrum with +/-   (or phase)



I have found the problem (Thanks to Federico Larroca) and with modifications the diagram works (below) but I still would like to know the previous question




Maybe it is just that I don't understand some things (or a lot of).....  my mathematics knowledge for DSP is far from awsome  ;-)


regards

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