Abstract: Resistivity mapping apparatus includes a tow mechanism for use by a human operator in moving the mapping apparatus over a surface and measuring the resistivity of soils of the surface. The tow mechanism includes a generally triangular shaped tow ring which is engageable by the operator's battery belt, harness, or pack-frame, the tow ring having two opposing hooks at a vertex of the tow ring for receiving a loop from a tow line. The tow line engages the tow ring and a cable depressor weight which keeps the resistivity mapping apparatus in close proximity to the earth as the apparatus is towed. A communication cable in the tow line preferably comprises an optical fiber which transmits signals from the receiver to a data logger carried by the operator.

Abstract: The location of underground objects such as pipes and conduits are located by detecting electrical signals emitted by the underground objects where the radiated signals include spread spectrum modulated RF signals. The system can operate in a passive or active mode, and in the active mode pseudo-noise (PN) generators can be employed or frequency-hopping can be employed. The use of spread spectrum minimizes or eliminates conflicting signals radiated from a plurality of underground objects and can improve signal to noise ratio of the detected signals.

Abstract: Material resistivity measuring apparatus includes a transmitter for transmitting a measurement frequency current through the material to a receiver spaced from the transmitter. The transmitter includes a power amplifier wherein the measurement frequency current is amplified in discrete steps depending upon resistivity of the material. The current level of the transmitter is transmitted to the receiver by modulating the measurement frequency current by a modulation signal whose phase is indicative of power level. The measurement frequency current can be modulated by a second modulating signal which provides a reference phase for the first modulating signal.

Abstract: A self-supporting radome construction is formed from a random distribution of four basic structural elements assembled in a standard reoccurring pattern. The elements define four basic triangular openings. Each triangular opening is covered with a panel, and only four panel sizes are required whether or not the interior surface is the same or different than the exterior surface.