And so, in the department of "ancient things found in the attic", here is a clipping from the Adelaide Advertiser in Australia. In 1986 I hadn't the slightest idea how important random numbers were, but they seemed fun at the time. Back then, I just wanted to do better than what a basic IBM PC would produce if you asked it to run a pseudo-random number generator.
Unfortunately no, a random number generator based on mashing together multiple radio stations won't work. Radio waves aren't truly random no matter how many we mash together, and there are mathematical ways to show that. It is an important problem to solve, which takes more maths than I currently have.
Dr Mads Haahr of Dublin has all the right mathematics to assess what is a good source of randomness, and he too looked to the air for his solution, but he chose to use static. "The first version of the random number generator was based on a $10 radio receiver from Radio Shack."
Dr Haahr founded Random.org to produce high-quality random numbers for "holding drawings, lotteries and sweepstakes, to drive online games, for scientific applications and for art and music." The theory behind his work is important for all random numbers. Since the topic of random numbers immediately brings up security, I need to point out that random.org is a single source of failure, and since the source code is not published it is not easily possible to verify Dr Haahr's claims of randomness (it could, for all we know, be a clever fake that slightly weights the random numbers this way or that, to the long-term benefit of whoever did the weighting.)