Abstract: The method of and apparatus for changing the inductance of a high power air core coil through the process of selectively shorting out predetermined numbers of turns. The apparatus comprises a conductive belt which is positioned interior the coil whereby the problems of corona discharge from the winding contents are substantially reduced. Since the shorting conductor is a thin film of conductive material attached to a tape, the mass is very low and vibration forces applied to the unit have much less effect in producing interruptions of contact.