1. A passive entry system for a vehicle of a particular model, said vehicle having an interior and an exterior, said system comprising: an internal antenna disposed in said interior; an external antenna disposed in said exterior; at least one amplifier driving at least one of said antennas and having a configurable gain; and a controller coupled to said amplifier for transferring at least one of internal and external software-configured gain values to said amplifier for controlling a transmission power of interrogation signals broadcast by said internal and external antennas, respectively, said software-configured gain values being obtained in an advance calibration procedure with respect to said particular model of said vehicle.