A handpiece (32) defines a bore (62) in which a proximal end (56) of a catheter or other interventional instrument (30) is received. An insulating support (70) supports an interventional instrument which carries an interventional instrument winding (54) in, but spaced from, the internal bore (62). A handpiece winding (64) disposed along the bore interacts with the transmission line winding (54) to form an inductive coupling with the transmission line. AftePH012096r the handpiece is slid axially to adjust the inductive coupling between the windings (54, 64), 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.
