Online Resources
Here are some resources that I have found useful:
Textbooks
Math
Physics
Electronics
Lessons in Electric Circuits (Kuphaldt, 6-vol. OER)NEETS Module 10: Wave Propagation, Transmission Lines, and Antennas (USN)Electromagnetics, Vol. 1 (Ellingson, Virginia Tech)Electromagnetics, Vol. 2 (Ellingson, Virginia Tech)Engineering Electromagnetics, 9th Edition (Hayt & Buck)Electric Circuits Eleventh Edition (Nilsson & Riedel)Op Amps for Everyone (TI, MIT)Op Amp Applications Handbook (Analog Devices)Analog Devices MT-series tutorialsMicrowave & RF Design (Michael Steer; open edition)
Antennas
ARRL Antenna Book, 21st editionAntenna Theory: Analysis and Design (Balanis, 4th edition)Antenna Engineering Handbook (All Versions). Authored by Johnson and Jasik (4th edition is by Volakis)USMC Antenna HandbookNIST antenna gain measurement notes