Since I spent a lot of time in Air Force radio, some time in AF intelligence, and being generally interested in communications (I have an extra-class Amateur Radio license) this book was right down my alley. Additionally, being interested in post WW2 British aircraft is also a plus with this book.
The theme here is airborne ELINT, electronic intelligence. You can learn a lot by listening to what the other guy is saying on the radio when the fighters are up and practicing interceptions or tactical support. And that’s where the British started after World War 2. When you’re flying at 20,000 feet you can hear a lot more UHF and VHF signals because these frequencies are line-of-sight communications. The higher you are, the further you can see and hear.
Up until about 1949, RAF ELINT consisted of listening to the radio communications. Everything else was considered as “noise”.