The scarcity of radio spectrum would not result in a single radio broadcast corporation monopolizing the spectrum.
What are you basing that assertion on?
Ever hear of pirate radio? Do you understand that broadcast power falls off with the square of the distance?
How do you envision a monopoly arising from the scarcity of the radio spectrum, when all sorts of other scarce resources do not create monopolies?
Who's to say the "steady state equilibrium" wouldn't be the one guy with the most powerful transmitter drowning out every other signal?
Too big a country, and Inverse Square Law for radio broadcast. How much do you think it costs to put down the most powerful transmitterS across the entire country? How much do you think it costs to continually run it at a rate that will drown out any potential competition? Don't you think the Law of Diminishing Returns kicks in at some point?
I submit it is easier to create a cable monopoly than a radio monopoly due to its higher barriers to entry. Building a transmitter is far easier than digging up a bunch of land to lay down cable. And we see that cable monopolies rely on government enforcement to actually have a monopoly.
Don't get me wrong. I am in no way saying that government granted monopolies are good or desirable. I was merely trying to point out it was possible for monopolies to form without a specific government mandate.
Yet, no one can ever point to a single "natural monopoly" actually becoming a monopoly "naturally".
"natural monopoly" is really just an argument that we should create a government monopoly because it's more efficient than the alternative. Perhaps. But monopolies are not a natural phenomenon. The nature of Nature is competition and ecological niches.