Abstract: An electromagnetic gradiometer (EMG) survey kit includes a lightweight man-carry boom about ten feet long. Matched magnetic dipole antennas are attached at each end and connected to a differential EMG receiver able to make measurements in the picoTelsa range. A pair of staging tripods allow the man-carry boom to be prepared for field use and assist the user in positioning themselves under a shoulder sling. An air core transmitter loop antenna and a low frequency square wave generator are spotted nearby a survey on the ground surface. Its emissions will illuminate any underground conductive structures with primary electric field waves. These in turn will reradiate near field magnetic waves that can be detected by the EMG receiver while walking around in a search area on the ground surface. GPS navigation receivers are used to locate and log the changing positions of the EMG receiver and stationary loop transmitter.

Abstract: A municipal infrastructure maintenance system uses a ground vehicle to move an antenna array in back-and-forth sweeps over large areas or distances. The antenna array comprises dozens of compartmentalized radio dipole antennas arranged laterally, shoulder-to-shoulder across the width of each sweep. An antenna switch matrix is connected between the antenna array and a ground-penetrating-radar (GPR) set and provides electronic aperture switching and selection, and the ability to laterally register one sweep to the next. The antenna array is extended out in front of the ground vehicle on a pivotable boom, and the cantilevered weight is a primary concern. The antenna array is constructed with aluminum-on-aluminum honeycomb panels slotted and folded around dozens of resistive-card compartment separators. Printed circuit boards with matching baluns are also slotted to receive tabs on the resistive cards, and their dipole elements are resistive loaded to quench crosstalk and near field effects.

Abstract: An electromagnetic gradiometer (EMG) survey kit includes a lightweight man-carry boom about ten feet long. Matched magnetic dipole antennas are attached at each end and connected to a differential EMG receiver able to make measurements in the picoTelsa range. A pair of staging tripods allow the man-carry boom to be prepared for field use and assist the user in positioning themselves under a shoulder sling. An air core transmitter loop antenna and a low frequency square wave generator are spotted nearby a survey on the ground surface. Its emissions will illuminate any underground conductive structures with primary electric field waves. These in turn will reradiate near field magnetic waves that can be detected by the EMG receiver while walking around in a search area on the ground surface. GPS navigation receivers are used to locate and log the changing positions of the EMG receiver and stationary loop transmitter.

Abstract: A stray-wire sensor includes a vertical magnetic gradiometer (VMG) carried over the surface by ground vehicles or by low-flying aircraft. The VMG has a spot of sensitivity on the ground which stays nadir to the VMG itself. A Faraday shield surrounding the VMG screens out the near field electric dipole signals, and a ferrite rod core and winding inside act as an antenna sensitive to the near-field magnetic dipole signals which radiate from horizontal lying stray wires on the ground surface in the dirt of hidden by ground cover. The VMG depends on it being moved around over the ground so that magnetic signal gradients and reversals can be measured point-by-point. The nadir points which fall over a point along a long horizontal wire will express characteristic signatures in the signal gradients and phase reversals measureable in the antenna.

Abstract: A municipal infrastructure maintenance system uses a ground vehicle to move an antenna array in back-and-forth sweeps over large areas or distances. The antenna array comprises dozens of compartmentalized radio dipole antennas arranged laterally, shoulder-to-shoulder across the width of each sweep. An antenna switch matrix is connected between the antenna array and a ground-penetrating-radar (GPR) set and provides electronic aperture switching and selection, and the ability to laterally register one sweep to the next. The antenna array is extended out in front of the ground vehicle on a pivotable boom, and the cantilevered weight is a primary concern. The antenna array is constructed with aluminum-on-aluminum honeycomb panels slotted and folded around dozens of resistive-card compartment separators. Printed circuit boards with matching baluns are also slotted to receive tabs on the resistive cards, and their dipole elements are resistive loaded to quench crosstalk and near field effects.