Reflection and transmission coefficients are important parameters of a wave‐guide junction. It is shown that these parameters in phase as well as in magnitude may be read directly from a graph. A short‐circuit is moved in one of two wave guides that are connected by the junction, and the corresponding reflection coefficient is measured in the other wave guide as in a standard method. The positions of the short‐circuit, however, are taken equally spaced every ⅛th of a wavelength. When plotted in the complex plane, the corresponding reflection coefficients fall on a circle and the chords joining opposite points intersect at a point that is simply related to the desired parameters.When very accurate measurements are desired, 8 or even 16 short‐circuit positions spaced at116thor132thwavelength can be used. The quality of the chord intersection then gives a control of the experiment by showing systematic or random errors. When the intersection is not perfect, because of random errors, a method of averaging is described that reduces these errors.