A handpiece defines a bore in which a proximal end of a catheter or other interventional instrument is received. An insulating support supports an interventional instrument which carries a transmission line winding in, but spaced from, the internal bore. A handpiece winding disposed along the bore interacts with the instrument transmission line winding to form an inductive coupling with the instrument transmission line winding. After the handpiece is slid axially to adjust the inductive coupling between the handpiece and windings, a locking mechanism functions in such a manner that the interventional instrument is inhibited from axial sliding motion relative to the handpiece while permitting rotation of the interventional instrument relative to the handpiece thus maintaining the inductive coupling while allowing optimal handling of the device.
