"You are incorrect. Most universal remote controls do not use radio frequencies. They use infrared, which is a completely different thing. " -tfabris

They are both electromagnetic waves and only differ in wavelength and frequency. So an infrared wave is just a really high radio wave. They only have different names for convenience of refering to different sections of the spectrum.

But the FCC probably has a certain range of radio frequencies allotted to remotes and a certain range of infrared frequencies allotted to remotes so of course they wouldn't be compatible with eachother.