The spectrum of a frequency modulated signal must be determined using Bessel Functions. Applet below shows how this can be done. The first 9 Bessel functions are plotted in the applet.

On the right values of Bessel functions 0 to 20 are printed for a value of m set by the scrollbars 2 to 5.

To find the sideband amplitudes for any m, m should be set by the scrollbars and the sideband amplitudes are immediately shown.

Image below shows how the applet appears. J0 which corresponds to the carrier is ~0 when m = 2.40482556

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