If you have more than one receiver, the main issue is time sincronisation between the receivers.
Using the two transmitters will complicate things a lot
Carl also references Plato's Republic when visiting the actual cave where Plato lived.
Carl also references books classical mechanics but not the book the parent comment mentions but earlier ones like Al-Baghdadi, Cristian Huygens, Galileo, Newton.
Halfway in the video he mentions the MIT (or Stanford) course of a professor who recently died. That course is online and has a lot of documentation (much better than this course.
Build Your Own Drone Tracking Radar: Part 1 https://www.youtube.com/watch?v=igrN_wd_g74&t=292s
You can contact me if you want more guidance. For passive radar you can just start with recorded data. I have access to huge amount of recordings on the Ukraine battlefield. Buying or building cheap antennas and radios is not needed for passive radar software development.
Radar was developed during the last two years of WOII, mainly in Boston at MIT and hundreds of companies each building a radar, most were deployed months later to win the war. Development after the war shifted to Silicon Valley, founding Silicon valley and the later chip and software startups decades later.