USA As Represented by Secretary of the Navy

John G Hoffman

Peder M Hansen

Elwin W Seeley

Wesley A Andrew

Gaylon E Ryno

Method and apparatus for detecting tunnels, voids or other anomalies bene an area of the earth's surface wherein an oscillator couples a current into two conductors laid parallel to each other to generate two magnetic fields in the earth beneath the area. The magnetic field is measured along a line midway between the two horizontal conductors to detect for an increase in the measured field which is an indication of the presence of an anomaly.

Method for rapidly detecting subterranean tunnels by detecting a

A continuous slot antenna having a rectangular waveguide whose broad dimeon varies in proportion to the attenuation for providing improved radiation patterns.

Variable waveguide continuous slot antenna

Improved method and apparatus for detecting anomalies beneath an area of earth's surface wherein an oscillator couples a current into two conductors laid parallel to each other to generate two magnetic fields in the earth beneath the area. The magnetic field is measured along a line midway between the two horizontal conductors to detect for an increase in the measured field which is an indication of the presence of an anomaly.

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San Diego, CA, United States of America

John G Hoffman