Special Relativity ain't that complicated at the level of algebra. When a body moves, its time becomes longer, and its length (at the direction of its movement) becomes shorter. It contracts by a factor called Gamma which equals:
(1-beta^2)^-0.5

where beta=v/c - the fraction of light speed the body reaches. beta<=1 and thus Gamma>=1.

That's all. As for the computation, I leave it as an exercise to the reader, since I have to run back to my boring lecture...

Anyways, since we're talking about Frequency Modulation (FM) radio transmission, these changes might distort the signal, though I've only learned AM yet, so any clarification by an electricon would be nice.