Vehicle information (e.g., status information, calibratable parameters, or diagnostic data) is transmitted from a base station mounted in a vehicle to a portable RKE fob via a radio-frequency signal within a specified average field strength limit. A multi-byte vehicle message is formed and then coded into a multi-bit coded message. The multi-bit coded message is framed into a plurality of packets. The radio-frequency signal is wirelessly transmitted from the base station with a plurality of spaced packet windows having a predetermined duty cycle, each packet window including a respective one of the plurality of packets. The radio-frequency signal within each of the packet windows has a predetermined field strength greater than the average field strength limit and a substantially zero field strength between the packet windows. The predetermined duty cycle results in an actual average field strength for transmitting all of the packets not exceeding the average field strength limit.