Abstract: A target junction is illuminated with energy at a fundamental RF frequency and reflections from the non-linear junction are analyzed to determine the type of junction detected. The power output level of a transmitter emitting the illuminating signal is automatically controlled so as to drive the signal strength of the received signals towards a predetermined value, e.g. a minimum threshold value. An indication of the current received signal strength, adjusted by a factor so as to compensate for any automatic adaptation in the actual transmitter power output level, may be provided to an operator.