depends if your power cable is made of shielded wire or not AFAIK.
Wrap the power cable in tin foil, should insulate it.
tin foild has to have a dc voltage applied to it......simply wrapping wont do the job, well wont do much anyway, 'grounding' cables ie the sheath means to mask with a linear magnetic field associated with dc voltage.
ali one rule with car ICE is always run power cables opposite side of car to speaker cables, same applies to arial's........
phones, wireless modems, tube lights, all affect reception.
try a signal booster.....