Radio age (Jan 1927-Jan 1928)

RADIO AGE for January, 1927 The Magazine of the Hour IS Washington Monument Does a Radio Shimmy Radiates at Third Harmonic of NAA Transmitter By S. R. WINTERS 4 TREES, bridges, enbankments, streams of water, trolley lines, valleys, large screens, water towers, and other surrounding objects are likely to exercise a distorting influence on radio waves. In effect, this means that if you are one of the millions of radio fans using a coil or loop of wire for radio reception, the directional properties of this pick-up system are effaced. Any one of the above-named objects, when interposed between the transmitting station and your radio receiving set, may cause the wave to deviate from its true course. Such distortion, other than invalidating the use of a loop antenna in determining the direction of a particular transmitting station, does not operate to the detriment of broadcast listeners. However, when coils of wire are employed as radio direction-finders, the distorting effect of surrounding objects must be systematically avoided or the causes of such wave deviations taken cognizance of and included in direction-finding calculations. Instances of proof may be cited : The United States Navy, before establishing radiocompass stations, investigates any objects that might cause radio waves to swerve from their path of rectitude ; similarly, the Navy must ascertain the distorting effect of metal in a hangar for a huge dirigible, like the Los Angeles, on which a radio compass is used. The Radio Laboratory of the Bureau of Standards is called upon to make all kinds of tests to determine the twisting influence of radio waves as caused by objects interposed in their path. The Lighthouse Service, with its radio beacons and their far-reaching implication of service, may request of the Bureau of Standards assistance in determining suspected deviation of waves which would invalidate the effectiveness of direction-finders in taking bearings from radio beacons. Again, the United States Coast Guard, in its recent adaptation of radio direction-finders in trailing rum smugglers, may need to know if the shore line of a river or a concrete bridge is undermining the directional characteristics of these direction finders. Study Distortion Influences THESE suggested services, together with the ever-increasing applications of the radio direction-finder, as well as the loop antenna with our radio receiving sets, place added emphasis upon results of original investigations conducted by the Radio Laboratory of the Bureau of Standards entitled "A Study of the Surroundings Upon the Indications of a Radio Direction Finder." And, while these comprehensive investigations in the field were made some time ago, this writer is fortunate enough to be able to present exclusive information, photographs, and charts disclosing the interesting results. Francis W. Dunmore and Morris S. Strock negotiated this study for the Federal government, exploring into the secrets of trees, bridges, banks of rivers, valleys, and trolley lines. Even the Washington monument, towering in silent majesty to a height of more than 500 1 Washington Monument whose fundamental is set into oscillation when NAA transmits feet, did not escape the searching eye (magnified by a telescope) of these government scientists. And, stranger than fiction was the revelation coaxed from this enduring shaft of marble. It not only has a natural wave length — about 625 meters — but when NAA, the naval station at Arlington, is broadcasting on 2,500 meters, the Washington monument is, in effect, a secondary radio transmitting station. For, we have the words of Francis W. Dunmore, eminent radio engineer and physicist of the Bureau of Standards, as authority for this conclusion. He says: "In this connection it is interesting to note that when the Arlington station was transmitting on. 2,500 meters, the signals could be heard on about 800