Colyn- alot of the auto HID are noisy due to the voltage conversion in the ballast. Be sure ground the ballast with a separate ground wire to a good ground.The purists say all the way to the negative of the battery, but that is prohibitive simply by the volume of everyone wanting their ground wire to go to battery neg. I usually put a block near the battery for these. The other noise from these ballasts is emitted. If they're mounted in the wings, then the emitted noise might be far enough away, If they're closer to the fuselage or getting on the antennas themselves you may need to enclose them in a Faraday cage , grounded metal box.