A direct coupled resonator filter having a plurality of resonant cavities (15) which are separated by means of inner walls (18). Coupling means (16) couple two adjoining resonant cavities (15). The coupling means (16) are located in a slot (20) which is defined in the inner wall (18). A portion of an edge of the slot (20) has electric contact with the coupling means (16). Generally, this portion of the edge of the slot (20) is a horizontal edge surface of the inner wall (18). It should be noted that the coupling means (16) are perpendicular to a vertical plane defined by the slot (20).