Why is the FFT magnitude of a signal with two frequency components, of equal amplitude not equal for both frequencies?

Why is the FFT magnitude of a signal with two frequency components of equal amplitude not equal for both frequencies?

Answer 1

[MathWorks Support Team]

The reason the FFT magnitude is not the same for a signal with two frequencies of the same magnitude is because the FFT is calculated at discrete points. Therefore, if the frequency of interest is not represented exactly at one of the discrete points were the FFT is calculated, the FFT magnitude will be lower.

For more information about this subject, see the attached Tech Note 1703, " What is the Proper Scaling of FFT Magnitude for a Signal with Two Frequencies?"