This is really cool online PDF that I found from another forum out there dedicated to CB radio showing the transition from 23 to 40 channel citizen band radio and how it was evolving. It goes into great detail over new crystal control circuits, rules and regs, the past and future of CB back then. Lots of detailed information on the internals of CBs back then and how they worked. I enjoyed reading through it a lot. Makes me miss this magazine so much since I grew up with Popular Electronics and found dozens of those mags from the 80s in the 90s, and then subscribed through their transition from Popular Electronics to the new name Poptronics, and saw their demise Either way good read, enjoy.. www.americanradiohistory.com/Archive-Hobbyist-Specials/Popular-Electronics-Communications-Handbook-1977.pdf