Noisiest RF band for random number generation
This is not likely to be a good method to generate random numbers -- at least not on its own, without significant additional analysis.  You need a source of random numbers that is not only noisy, but also unpredictable to an adversary.  It's not clear that radio will meet that need.  If you listen on a FM band, an adversary who is nearby can also listen on the same FM frequency and will likely see something very similar to what you see, so will have a huge leg up in predicting the numbers you generated.

Bottom line: don't try to roll your own random-number source.  It's better to use a time-tested scheme, like a crypto-strength hardware RNG, or /dev/urandom, or a similar crypto-strength scheme.