A power circuit of a coil, includes two power or transmission line segments that are each connected to one of two ends of this coil, the line segments forming with the coil an oscillating circuit exhibiting a determined resonance frequency. The circuit has two line segments each including at least two conductors, of which one is connected to coil, and between them exhibit identical structures and identical lengths of connected conductors, whereby this common length is essentially a multiple of half of the resonance wavelength of the oscillating circuit. The conductors which are connected to coil at one of their ends are connected to one another at their other end by an adjustable symmetrical tuning component that completes this oscillating circuit, which with symmetrical structure is powered by a primary power circuit.