Electromagnetic waves travel through a vacuum with a speed c that is independent of their wavelength. Thus (from Fourier theory) a wave of arbitrary shape will propagate without distortion. Such dispersion free propagation is unusual. In general, the components of a wave group travel at different speeds and the group spreads out as it propagates. For example, waves travelling through a medium or down a cable can suffer dispersion. Here we consider dispersion in the context of transmission lines.