It's always nice to see RF and Signal Processing stuff on HN.
If you're seriously interested, download Octave (Matlab replacement) and write a program from scratch to simulate a BPSK system and generate a "waterfall" (bit error vs. noise) curve. Don't stop until you can get your curve to perfectly match the one in a text book . By doing this, you will learn about modulation, demodulation and and "Additive White Gaussian Noise" (AWGN) channel models. If you can get the waterfall curve to match exactly, you will also be covering concepts such as "energy per bit". A BPSK should be quite doable for an amateur.
Once you have the BPSK simulation, try extending your simulation in different directions and matching the textbook curves. The following challeges are roughly in order of increasing difficulty
1) Add a block code, such as Hamming or BCH.
2) Replace the simple AWGN channel model with a Rayleigh or Ricean model
3) Add a convolutional code (with Viterbi decoder)
4) Implement Orthogonal Frequency Division Multiplexing (OFDM)
5) Implement an LMS receiver
6) Implement a Low-Density Parity Check code (use the one from the WiFi standard)
7) Implement a complete 802.11a simulation
8) Implement a complete DVB-T simulation
9) Implement a MIMO system, assuming perfect channel knowledge
10) Implement a MIMO system with channel estimation
Get to number 10, and you will know more about radio signal processing than most engineers.
 eg. "Lin and Costello" Error Control Coding or "Proakis" DSP
there is the canonical Fundamentals of Wireless Communication (https://people.eecs.berkeley.edu/~dtse/book.html) which is pretty good. also, iirc, there is a book by oppenheim as well (signals and systems, i think)
edit-00k : yes, oppneheim book is called 'signals and systems' and it is available on ocw as well (https://ocw.mit.edu/resources/res-6-007-signals-and-systems-...)