Here is a YouTube video about Passive RADAR using RTLSDR, and is part of a growing collection of videos I have found to be useful. The reason is development of passive radar dsp code for better resolution and range and understanding science related to software defined radio.
This tutorial, "Passive RADAR using RTLSDR" is free education you can watch, which will help you deepen your knowledge and be better prepared for licence exams, schoolwork, or operating radio equipment.