Abstract: An obstacle avoidance system for obstacle detection in an opaque material. The system includes at least one electromagnetic signal source adapted to produce an electromagnetic source signal suitable for transmission through the opaque material, at least one electromagnetic signal detector adapted to receive reflected electromagnetic energy signals from discontinuities in the opaque material encountered by the electromagnetic source signal, and a reflected electromagnetic energy signal processor suitable for determining a presence of obstructions and/or strata variations within the opaque material. The system is preferably integral with a head element suitable for traversing the opaque material, for example a subterranean drill bit.

Abstract: An underground telemetry system having an antenna system having at least one metallic radiating element having a single or a dual top loaded folded monopole configuration and disposed within a metallic housing and having RF electronics to self-calibrate and tune the input impedance of the antenna elements.