Reception Experiments in Mount Royal Tunnel

This paper deals with certain experiments carried out in the Mount Royal Tunnel of the Canadian National Railways at Montreal, Quebec, in order to determine how radio waves reach the receiving set. Preliminary experiments in 1926 indicated that the penetration of radio waves into the tunnel was a function of the frequency, short waves below 100 meters dying out within a few hundred feet of the mouth of the tunnel. More exact experiments and measurements were planned and carried out in 1928 to bring out the part played by the wires, cables, and rails leading into the tunnel. The tunnel mouths were blocked and the cables grounded, and the results so obtained indicated that the effect of cables and rails was also dependent on the frequency. It was also evident that more actual energy entered via the tunnel itself than was at first suspected. The effect of rails and cables is not a simple one but involves loop action, wave-antenna effects, and re-radiation. Curves are attached showing graphically the results obtained. A map of the area and an elevation of Mount Royal itself give general details of the geology of the region.