Historic These are classic papers, that represent key advancements in radio technology. It is neither authoritive or complete, buy still interesting in my view.

SDR One of the most important developments in radio in recent times. There are lots of possible links to add, but these are a few that I think are readable explanations of what is otherwise a dry mathematical subject.

Python Not wishing to get into flame wars about programming languages, this is an unabashed plug for one option. I discovered Python over 20 years ago and gave up on all other programming for the simple reason that I found that it helped me get things done. Then running a small business, the fact that it is absolutely free, has a tremendous libraries with a vibrant and helpful community just solidified that choice.

Books Not strictly speaking downloads, but these are a few non-technical books about technology that I have found a good read. I hope you do as well.