Passive radiofrequency transponder intended to be integrated into a mass made of elastomer blend, comprising: - a radiating dipole antenna consisting of a single-strand helical spring having an axis of revolution, a median plane, a winding diameter (D1, D2), a helix pitch (PI, P2) and a wire diameter defining the inside diameter and outside diameter of the radiating antenna, the length of which is suitable for communication in a frequency band with a radiofrequency-transmitting reader, - an electronic portion located inside the radiating antenna, comprising: i. an electronic chip, ii. a primary antenna electrically connected to the electronic chip and electromagnetically coupled to the radiating antenna, iii. said primary antenna having an axis substantially parallel to the axis of revolution of the radiating antenna, iv. said primary antenna having a median plane which is substantially superposed with the median plane of the radiating antenna, v. said primary antenna being circumscribed by a cylinder the axis of revolution of which is parallel to the axis of the radiating antenna and the diameter of which is larger than or equal to one third of the inside diameter of the radiating antenna, located plumb with the primary antenna, characterized in that, in a first region (101, 101a, 101b) of the radiating antenna, in which the radiating antenna is not located plumb with the electronic portion, a first pitch of the radiating antenna corresponding to the helix pitch of the radiating antenna in this first region (101, 101a, 101b) is larger than the second pitch of the radiating antenna corresponding to the helix pitch of the radiating antenna in a region in which the radiating antenna is located plumb with the electronic portion. - a radiating dipole antenna consisting of a single-strand helical spring having an axis of revolution, a median plane, a winding diameter (D1, D2), a helix pitch (PI, P2) and a wire diameter defining the inside diameter and outside diameter of the radiating antenna, the length of which is suitable for communication in a frequency band with a radiofrequency-transmitting reader, - an electronic portion located inside the radiating antenna, comprising: i. an electronic chip, ii. a primary antenna electrically connected to the electronic chip and electromagnetically coupled to the radiating antenna, iii. said primary antenna having an axis substantially parallel to the axis of revolution of the radiating antenna, iv. said primary antenna having a median plane which is substantially superposed with the median plane of the radiating antenna, v. said primary antenna being circumscribed by a cylinder the axis of revolution of which is parallel to the axis of the radiating antenna and the diameter of which is larger than or equal to one third of the inside diameter of the radiating antenna, located plumb with the primary antenna, i. an electronic chip, ii. a primary antenna electrically connected to the electronic chip and electromagnetically coupled to the radiating antenna, iii. said primary antenna having an axis substantially parallel to the axis of revolution of the radiating antenna, iv. said primary antenna having a median plane which is substantially superposed with the median plane of the radiating antenna, v. said primary antenna being circumscribed by a cylinder the axis of revolution of which is parallel to the axis of the radiating antenna and the diameter of which is larger than or equal to one third of the inside diameter of the radiating antenna, located plumb with the primary antenna,