Geophysical Survey Systems, Inc.

Henny F Harmuth

A radiator useful for radiating pulses with a duration of about 10 ms is disclosed. Such pulses occupy the frequency band from zero to a few hundred Hertz. For a given time variation of an electromagnetic signal, the energy radiated in the far field is proportional to (Is).sup.2, where I is the current amplitude in the antenna and s is the length of the radiator. Typical antenna designs cannot be used at very low frequencies with large relative bandwidths. However, the large current radiator disclosed, herein, is small, has antenna currents in the order of 10.sup.8 A, and requires a drive voltage of about 1 volt and drive current of 10.sup.4 A. This large current radiator is designed with a small antenna length s by using a design wherein the antenna current is n times larger than the drive current. This is accomplished by winding electrically conductive means n times around a shield so that the n forward loop wires are all on one side of the shield, and cover a surface area sxW. The n return loop wires are on the opposite side of the shield and are confined so that they cover a surface area that is very small compared to the area of the forward loop. Furthermore, the shield is fabricated to reflect the electromagnetic energy produced by the forward loop and absorb the electromagnetic energy produced by the return loop. Hence, the antenna is highly efficient. And, since n can be 10,000 or more, the antenna current can be in the kilo Ampere range and beyond with a moderate drive current.

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Potomac, MD, United States of America

Henny F Harmuth