Development of a Ground-Conductivity Map for the Area of the Federal Republic of Germany from Measured Field-Strength Contours,
INSTITUT FUER RUNDFUNKTECHNIK G M B H MUNICH (GERMANY F R)
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Resolution 73 of the International Radio Consultative Committee CCIR urgently requests ground-conductivity information at 1 MHz for planning purposes in form of suitable maps. Following that request 1201 propagation paths with a total length of 92578 km were derived from daytime field-strength contours of 47 MF-transmitters at 33 transmitter sites in the Federal Republic of Germany. Assuming a constant antenna efficiency of 70 the field-strength values at the receiving terminals of these propagation paths were normalized to the conditions which form the base for the propagation curves in the Annex of CCIR Recommendation 368-4. From the propagation curves mentioned before the related ground-conductivity values were taken for the given values of receiving distance and field-strength. A comparison of ground-conductivity values found for 14 transmitter sites with two frequencies showed a linear relation between the effective ground conductivity and the frequency. On this basis all conductivity values were normalized to a frequency of 1 MHz. The average ground-conductivity values for each transmitter were associated with four different geographical zones.
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