The dependence of beat strength on beat phase and frequency. For each band, we show three consecutive beat cycles, extracted near the peak of the orbital light-curve and phased on the beat ephemeris. Only the W1m BG and Z bands are simultaneous, and these have an arbitrary scaling in flux, for comparison with the radio data. The significant beat-to-beat variations in the emission are apparent, as is a slight offset in beat phase between the optical and radio bands. Colour coding is as in Fig. 10.