FFT Noise Problem

[mdufayet]

Hi !

I am trying to run a Fast Fourier Transform on the signal you see on the picture (red).

And I cannot have more samples of the signal.
So, I applied a butterworth and got the blue signal. I am expecting a peak around 1500 Hz (the supposed frequency of the blue signal) ... but I do not obtain that(at all:bang.
I also tried to do a "zero-padding" but it think that it changes to much the initial spectrum.

Anyone have an idea to get ride of this noise or reducing it largely ?

Thank you for your help !

 

[tendo R]

Can not see the picture.
Sometime this problem happens because your fft's noise is higher than your signal. Try more points.