Abstract: A measuring line for a coaxial conductor for determining energy throughflow and standing-wave ratio, comprising two coaxial connectors (2) having an impedance adapted for a coaxial conductor; an intermediate hollow conductor comprising an inner conductor (3) connected to the center conductor of the coaxial connectors and which is matched with that impedance; a directional coupler in the hollow conductor for taking-out two electric signals each corresponding to a respective propagation direction of electric waves between the coaxial connectors; and a detector circuit for respective electric signals. The directional coupler comprises a single directional coupler (4) which is mounted within the hollow conductor and parallel with its inner conductor (3) and which has symmetrically disposed branch lines (8) which are drawn through openings (9) in a wall of the hollow conductor and each of which extends to a respective strip conductor in a circuit board (10) mounted externally of the wall.