An investigation is made of the mechanics of the wave dispersion phenomenon obtained in a numerical simulation of the rotating annulus flow system. Wave dispersion is characterized by the presence of two quasi-steady sideband baroclinic waves of comparable amplitudes and different phase speeds. The recurrence of wavepacket formation downstream of the wave train can be kinematically related to the group velocity. The vertical structure of the temperature wave for the primary wavenumber consists of a upper layer and a lower layer maximum, while the secondary wavenumber lacks the lower layer maximum. The primary wave is baroclinically acieve as it is maintained by the zonal flow baroclinicity, while the secondary wave is baroclinically passive in the sense that it is linearly stable with respect to the instantaneous zonal flow, although it exhibits a strong baroclinic energy conversion. Wave-wave interactions enhance the baroclinic energy conversion of the secondary wave by increasing the pressure-temperature phase difference, counteracting the negative nonlinear energy transfer and the stabilizing effect of the zonal mean basic state.