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Observations of Coherent Backscattering of Hectometric Radiowaves from Along the Sea Surface

出版	U.S. Department of Commerce, Environmental Sciences Services Administration, Institutes for Environmental Research, Institute for Telecommunication Sciences and Aeronomy, 1967
URL	http://books.google.com.hk/books?id=vmn3rQEACAAJ&hl=&source=gbs_api

註釋Observations of coherent backscatter from the surface of the sea, at ranges up to 200 km, using a slightly modified ionosonde are described. The range of frequencies used was between 2.6 and 8.5 MHz corresponding to sea wave lengths of 58 - 17 m and periods of 6.1 – 3.3 sec. Lower frequencies could be used to observe sea waves of longer periods. Doppler shift of the scattered signals was proportional to the square root of the radio frequency, as expected on theoretical grounds. The bandwidth of the scattered signals observed on one occasion is interpreted as being due to about 30 long crested waves contributing to the signal. Observations using two “Beverage” antennas, each oriented at 45° to the coast, show that the amplitude of the scattered signal depends on direction. It is estimated that it may be possible to observe sea scatter regularly to distances as great as 400 km. If this proves to be the case, such observations might be of economic value to the shipping industries. Fishing boats and coastal shipping could use them to avoid areas of rough water.