An orthomode transducer and to a satellite transmission chain includes the orthomode transducer, for transmitting a first signal and a second signal in orthogonal propagation modes. The transducer comprises: a primary waveguide with a square or rectangular cross section, two guided access means having firstly a free end via which the first signal and the second signal are respectively injected or recovered, and secondly two arms connected to the primary waveguide. Each guided access means comprises a junction configured so as to connect the free end to the two arms of the guided access means, the two arms of each guided access means being connected to the primary waveguide at two off-centred locations on one or more sides of the primary waveguide symmetrically about an axis of symmetry of the primary waveguide.