Radio Broadcast (May-Oct 1922)

Record Details:

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RADIO BROADCAST the waves were distorted as much as 50 degrees, while at greater distances from this same trolley line the distortion became less until at points about 2000 feet away the distortion was entirely gone. This means that after passing a distorting structure the waves straighten out again and are not erroneous in their direction until other obstructions are met. It was found that the amount of distortion produced varied sometimes as a trolley car passed along the line and thus changed the point at which the trolley wire was connected through its motor to the ground. Near a large screen, such as is used as backstop for a tennis court, or near a large tree in an open field it is found that the distortion is in one direction when the direction finder is on one side of the object, while the distortion is in the other direction when the direction finder is on the other side. The distortion or bending of the waves is also found to differ when the transmitting station uses different frequencies or wave lengths. The wave length, which is subject to greater bending, depends upon the actual dimensions of the object which is causing this change in direction. When the direction finder was located on a large concrete bridge having steel reinforcement, a change in the direction of the radio waves amounting to as much as 14 degrees was observed. This bending of the waves became less as the direction finder was moved along the road away from the bridge in either direction. The distortion was found to be worse when the transmitting station was using a wave length of 400 meters than when it used longer waves. Similar results were obtained when the direction finder was placed in the vicinity of a telephone line or a low antenna of an ordinary radio receiving station. The distortion became greater as the direction finder was brought nearer to the wire. The distortion was in opposite directions as the radio direction finder was used at the two opposite sides of the wire, telephone line, or antenna. In the case of the antenna the distortion was found to be far greater when the antenna and receiving set system were tuned to the same wave length as that employed by the transmitting station whose signals were being observed. Among the most interesting tests of this series were those made in the vicinity of the Washington monument. This monument is built of stone, but contains an iron stairway and an elevator cable which are conductors of electric current. The Washington monument is 555 feet in height and is located in the centre of a large park which is comparatively free from other structures which might cause a change in the direction of the passing radio waves. By far the greater distortion of the waves was observed at points near the monument, changes of direction as large as 70 or 80 degrees being found at points as near as 1 50 feet to the base of the monument. When the direction finder was moved to a point 300 or 400 feet from the base of the monument the distortion was found to be only 5 or 10 degrees. In order to determine the wave length at which the monument caused the greatest Washington monument around which tests of the direction of radio waves were made. The natural wave length of the monument was found to be about 800 meters