A passive entry system for a vehicle of a particular model communicates with a portable fob that may be located in either an interior and an exterior of the vehicle. An internal antenna is disposed in the interior and an external antenna is disposed in the exterior. At least one amplifier drives at least one of the antennas and has a configurable gain. A controller is coupled to the amplifier for transferring at least one of internal and external software-configured gain values to the amplifier for controlling a transmission power of interrogation signals broadcast by the internal and external antennas, respectively. The software-configured gain values are obtained in an advance calibration procedure with respect to the particular model of the vehicle.