Apparatus, including a handle and a first conductive tube that is attached to and extends from the handle. The tube is biocompatible, and a tube distal end is configured to be inserted into an orifice of a human being for a medical procedure. The apparatus includes a second conductive tube, that is attached to and is enclosed by the first conductive tube. The two tubes together act as an antenna for electromagnetic radiation. An insulated conductive coil is fashioned around and is fixed to the second conductive tube, and the coil generates a signal in response to a magnetic field traversing the coil. The apparatus also includes a transceiver that receives the signal from the insulated conductive coil, and in response generates a radiofrequency signal at a preset frequency and conveys the radiofrequency signal to the second conductive tube for radiation therefrom as electromagnetic energy at the preset frequency.
