The present invention relates to a coupling element (21) by which the coupling of a resonator (24) is adjusted in a radio frequency filter. The coupling element of the invention is a strip made of flexible conductor material being shaped symmetrical relative to the normal, that is, the symmetry axis of the longitudinal axis extending via the centrepoint of the strip in the longitudinal direction. The strip (21) is fixed at least at two points of an edge in the longitudinal direction to the circuit board (25) either by surface mounting on pads (33, 35, 36) or by soldering into holes borred in the circuit board to be at appropriate space from the resonator coil (34) and from the surface of the circuit board (25). One (33) of the fixing points is grounded and another (36) is connected to the signal conductor in the filter. The coupling can easily be adjusted by bending the board relative to the symmetry axis either one-sidedly or on both sides.