AN IMPROVED EMERGENCY BEACON The present invention relates to an improved emergency beacon for rotorcraft and other aircraft. The technical field of the invention is that of fabricating rotorcraft. The present invention relates more particularly to an eroergency beacon adapted to be fitted to an aircraft provided with an antenna and to be connected to said antenna. It i» known to fit a helicopter with an antenna that is secured to the fuselage and that is connected to a radio transniitter as described foe example in patent FR 2 743 198. In particular, it is known to fit a helicopter vith an emergency beacon comprising a housing fitted with a connector and containing a radio transraitter and a connection member connecting the transmitter to the connector, the connector enabling the beacon, and its transmitter, to be connected either to an antenna that is secured to the helicopter, or else to a portable auxiliary antenna, That enables a person on board the helicopter, after an accident that has damaged the antenna secured to the helicopter, to connect the beacon to the auxiliary antenna, and where appropriate to take the beacon and the auxiliary antenna away from the helicopter so as to trigger or maintain transmission of an emergency radio signal by the beacon. The transmitter of the beacon can be activated as a result of an incident, such as an impact, being detected by a circuit that is connected to an impact sensor incorporated in the beacon, and/or can as a result of a human being taking manual action on a trigger member incorporated in the beacon, such as a svitch. US patent No. 6 411 2SO describes an antenna for an emergency beacon that is designed to transmit distress signals at three radio frequencies, i.e. 121.5 megahertz (MH2), 243 MHz, or 406.025 MHz. Patent No. FR 2 S60 09S describes a power supply device for a beacon that transmits at 406.025 MHz. Patent Mos. FR 2 776 391, FR 2 873 451, and JP 11 177 462 describe other characteristics and uses for emergency beacons. Emergency beacons for aircraft present drawbacks. In particular in the. event of the aircraft crashing, the antenna secured to the aircraft, the auxiliary cable, the cable (s) connecting said antenna (s) to the transmitter/ and/or the connector incorporated in the housing of the beacon can break or be damaged, which can limit or prevent the transmission of a distress signal. Furthermore, in particular in the event of a crash causing the antenna that is secured to the aircraft breaking