A fluorescent lamp, an arc discharge device, creates radio waves which may interfere with radio reception by direct radiation or by feedback through the power line if the radio and lamps are on the same circuit.
Since the radiated signal is extremely weak, this problem can be remedied by simply moving the radio a short distance (10 feet) from the light source.
If the interference is caused by feedback in the power line, a noise suppression filter will generally eliminate the problem. If the problem persists, separate branch circuits may be required for the radio equipment and lighting fixtures.
To meet FCC regulations, the radio interference filter is now built into the ballast.