Inductance of a shielded coil

Models are developed for the inductance of a helical coil and a helical coi l inside a conducting shield. Values of inductance are Pound from analysis. The dependence of inductance on the presence of the shield is assessed qua ntitatively and explained on the basis of physical principles, and the sign ificance of skin and proximity effects in the wire coil is outlined, The in ductance of an isolated, one-turn loop and a one-turn loop inside a conduct ing tube are measured and are found to be in excellent agreement with compu ted data. When the conducting shield and coil are very close, the inductanc e of the coil is found to be greatly diminished suggesting that one must ac count for the presence of shields when characterizing inductors, which migh t be used for loading and tuning of antennas, A nearby conducting shield mu st be accounted for in inductance calculations if reasonable accuracy is ex pected.