Abstract
We predict conductance oscillations in a quantum-anomalous Hall 2d strip having a superconducting region of length L_x with a chiral Majorana mode. These oscillations require a finite transverse extension of the strip L_y of a few microns or less. Measuring the conductance periodicity with L_x and a fixed bias, or with bias and a fixed L_x, yields the speed of the chiral Majorana mode. The physical mechanism behind the oscillations is the interference between backscattered chiral modes from second to first interface of the NSN double junction. The interferometer effect is enhanced by the presence of side barriers.