Variation of field strength in underground mine area on the size of VLF loop antennas laid on the Earth surface

A VLF loop antenna of moderate size laid on the Earth´s surface for underground mine communication does not carry a uniform current. As a result of the non-uniform current distribution, the field in the Earth medium is dependent on angular position with respect to the feed point in addition to radial distance and depth of the observation point. The present investigation shows the variation of the underground magnetic field distribution on the size of loop antennas laid on the Earth´s surface. The current in the surface loop is computed by the method of moments.