A plot of frequency against apparent DM in each of the observing bands. The circluar points show the DM obtained using a static template, and the triangular points show the DM from a frequency-dependent template based on our models of the pulsars’ pulse shape evolution. In each case (apart from that of PSR B1133+16) the model-based template provides a consistent DM across all frequency bands, while use of the static template often results in significantly different DM values.