that, and the fact that FM radio gets it’s name from “Frequency Modulated”; which means that there is a oscilator in your radio that modulates the radio waves at a sertain frequency corresponding to the radio channel you’re listening to.

but you would be able to do pretty much the same thing, if you’d record a long time of background radio emissions. though i’d assume recording on the surface (if you could survive on the planet surface that is) would yield far more sudden changes, as the probe recorded the noise from the entire planet (or the entire pole, if it was focused on the pole), where as you’d only record a small fragment of the sky.