Seeking Spectrum's Historical Picture

An interesting research project has fallen into my lap from a professor with whom I had a pretty cool class last semester. He seeks “historical visualizations” of spectrum, with an emphasis on how spectrum has been represented in the context of policy debates.
Quoth Christian Sandvig, “Here is a topic where people argue all the time about whether the spectrum is ‘full’ or ’empty’ (and about interference, whether things are ‘near’ or ‘far’, etc.) and yet the visual conventions that convey ‘fullness’ or ’emptiness’ or ‘nearness’ — how maps and diagrams and charts are made, with what shapes, at what scale — seems to be subject to a lot of cavalier manipulation.”
My task is to explore how this has occurred throughout policy-history, with deviation into related areas allowed if the graphics are compelling enough. It’s a somewhat daunting assignment because I can see getting lost in the hunt.