Abstract
MOST of the reliable measurements of the frequency stability of very low frequency (VLF) propagation paths have been made over the North Atlantic path, and over paths of the same order of length. Pierce et al.1 used atomichrons on each side of the Atlantic and found a standard deviation of 2 in 1011 for frequency comparisons consisting of 24 h averages for the GBR (Rugby, 16.0 kc/s) transmission over a path length of 5,200 km. It has been suggested by Watt and Plush2 that the standard deviation of phase—and thus of frequency over a constant interval of time—would be proportional to the square root of path length. However, Chilton et al.3 give figures suggesting that it may be proportional to the square of the path length squared.
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Pierce, J. A., Winkler, G. M. R., and Corke, R. L., Nature, 187, 914 (1960).
Watt, A. D., and Plush, R. W., J. Res. Nat. Bur. Stand., 63 D, 35 (1959).
Chilton, C. J., Crombie, D. D., and Jean, A. G., Propagation of Radio Waves at Frequencies below 300 Kc/s, 257 (Pergamon Press, Oxford, 1964).
Gerard, V. B., J. Atmos. Terrest. Phys., 28, 425 (1966).
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GERARD, V. Comparisons of Frequency by Long Path Very Low Frequency Transmissions. Nature 211, 1284 (1966). https://doi.org/10.1038/2111284b0
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DOI: https://doi.org/10.1038/2111284b0
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