Abstract: A pocket size antenna match indicator is described having a self contained modulated low level RF signal source which is applied to an antenna or other load under test through a dual directional coupler. Sampled RF reflected signals are detected, filtered and amplified to provide a DC voltage directly proportional to antenna mismatch. Easy to read measurement of VSWR is derived from the DC voltage by means of a dot display driver connected to a LED display.

Abstract: Coded binary signals are coupled to an automotive vehicle by a magnetic signpost embedded in a traversed roadway lane. The signpost includes polarity coded magnetic pole faces having vertically directed flux lines at differing spaced longitudinal regions along the lane. Pole faces are arranged so a flux null is between adjacent longitudinal regions. Differing signals are coupled to vehicles going in opposite directions in adjacent lanes by unambiguously coding the signpost in opposite directions and arranging the pole faces so that magnetic flux continuously extends across a majority of both lanes. A detector on a vehicle includes a magnetic field concentrator including a pair of vertically extending and aligned low reluctance magnetic pole pieces having an air gap between them, in which a Hall plate is positioned. The pole piece closest to the road has shorter length than the pole piece remote from the roadway.