How to locate exact frequency of peak in FFT spectrum

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In this video we are describing, how to locate the exact frequency of peak in FFT spectrum.
Some basic information for beginners:
Spectrum has the frequency range. Spectrum contains a number of lines.
Spectrum has the resolution, which is defined as the frequency interval between lines.
And here the problem begins. The spectrum lines are only limited number of frequencies.

Видео How to locate exact frequency of peak in FFT spectrum канала Adash