A subscriber device (10) includes one or more sensors (102) for measuring a object electromagnetic characteristic, such as conductivity, permittivity or permeability. A controller (104) stores the object electromagnetic parameter in memory (106) and, operating in accordance with a performance enhancement routine stored in the memory (106), enhances operation of the subscriber device (10) in accordance with the electromagnetic parameter. The controller (104) may do this by adjusting the power of an amplifier (112), the frequency of a synthesizer (114) or the impedance of an antenna (110). A software program controlling the subscriber device and a corresponding method are described.