a whole load of PDFs here to download and read. In spite of its title there are publications from most of the English speaking world (including AU and UKO) and they are not just about broadcast engineering but sound engineering and other electronics (mostly 20th century stuff but plenty of 1970s to 1990s info which is still valid today); there’s even scanned back issues of the UK’s Practical Wireless and Electronics and Wireless World from the 1980s (lots of hi fi stuff in there too)

AmericanRadioHistory.Com – Documenting the History of Radio TV and FM broadcasting