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Radiation of frequency 200 Mc/s. was transmitted through the covering rocks of certain railway tunnels from a radar transmitter feeding a special aerial. The object was to measure the attenuation of rocks in situ to see if there might be practical applications to geophysical prospecting. The attenuation in dry sandstone was found to be 3 to 4 db. per foot, which was much greater than had been hoped. It thus appears that the penetration is insufficient to be of practical use.
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R. I. B. Cooper (1948) studied this question.
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