Far be it from me to throw physics in here...
But magnetic fields have, to the best of my knowledge, absolutely zero effect on any form of pure electromagnetic radiation. They can be used to affect charged particles (ions, electrons, etc.), which is why your TV set works.
You could affect a radar transmission in some way by throwing magnets in front of it, but you would get exactly the same result if you stuck equally-sized blocks of dead iron in front of it.