Onboard vehicle communication device and portable identifyng device for communicating with it

The vehicle (1) has a central unit (2) with a radio frequency transmitter. An antenna of the transmitter sends an inquiry message with a carrier wave frequency less than 100 mega hertz, to a portable identifier (3). The antenna has transmission electrodes (5-10) coupled to the transmitter output. Each electrode is not in resonance with the frequency to radiate an electrical field in a transmission zone near the electrode. An independent claim is also included for a procedure for transmitting a signal between a vehicle equipped with a radio frequency transmitter, and a portable identifier equipped with a radio frequency receiver.