Spectral Leakage in layman's terms

1. What is meant by spectral leakage?
2. Why spectral leakage?
3. How do you deal with spectral leakage?
4. What is scalloping loss?

What is meant by spectral leakage?

Leakage, more explicitly called spectral leakage, is a smearing of power across a frequency spectrum that occurs when the signal being measured is not periodic in the sample interval.

Why spectral leakage?

Spectral leakage due to FFT is caused by: mismatch between desired tone and chosen frequency resolution, time limiting an observation.

How do you deal with spectral leakage?

We have seen that spectral leakage is reduced by tapering the digital signal by a window function before the DFT takes place. A generalization of this technique is the short-time discrete Fourier transform (STDFT).

What is scalloping loss?

The scalloping loss is the coherent gain of a frequency half a bin from a component on the DFT divided by the coherent gain of the window. From: Big Data in Astronomy, 2020.