Abstract
A ROTATING loop type of radio beacon was developed in Great Britain several years ago, and two stations employing this arrangement are still in use in connexion with aerial and marine navigation. The advantage of the system is that wireless bearings may be obtained at any receiving station merely with the aid of a stop watch or chronometer. The use of such a chronometer is rendered unnecessary in a new type of rotating beacon, which is described in a paper by U. Okada, published in the report of Radio Research in Japan of October 1934, vol. 4, p. 185. In this new system, a vertical loop transmitting aerial is used as previously, to give the usual ‘figure-of-eight’ radiation characteristic. Instead of rotating this loop continuously, however, it is swung backwards and forwards about a vertical axis through an arc of 180°. During its movement the speed of rotation is uniform and equal to one revolution per minute. The movement in each direction starts from a north and south position alternately, at each of which a characteristic morse signal is emitted. This signal is then followed during the rotation of the loop by a succession of 90 dots, at the rate of 1 dot for every 2°. By counting the number of dots from the starting point to the signal minimum, the bearing of the receiver from the transmitter may be calculated. The additional observation taken with the loop moving in the reverse direction enables the midpoint of a broad minimum to be accurately determined. Tests carried out in Japan on land and at sea have shown that an accuracy of observation of ±6° was obtained at distances up to 46 km. with an experimental beacon operating on a wave-length of 950 m. It is considered that by attention to details of the apparatus the maximum error could be reduced to 2°, which it is suggested is sufficient for most practical purposes.
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A New Rotating Radio Beacon. Nature 135, 539 (1935). https://doi.org/10.1038/135539b0
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DOI: https://doi.org/10.1038/135539b0