I'm a dabbler and I came across a very cool project that seemed a bit out of my league at the moment - but perhaps you and others on this thread will get a kick out of:

https://ocw.mit.edu/resources/res-ll-003-build-a-small-radar...

Basically, making your own radar system with Coffee cans. As a newbie, I'm a bit surprised by all the modular components that were just fitted together. I knew about Amps and attenuators but didn't know you could get VCOs and mixers like that too. Any books/website recommendations/beginner projects would be appreciated!