An object is to achieve a radio power transmitting system capable of adaptively controlling power transmission efficiency, and the following means for achieving it is proposed. A second tube having a cross section that is relatively small in relation to the cross section of the first tube and helical shaped section intermediate its ends is located within the first tube and extends through caps at the ends of the first tube to be received in headers. In the preferred embodiments, bonded surfaces are comprised of materials that are suitable for medical devices.