Dependence of beat strength on orbital phase and frequency. We show that the beat pattern is captured in short integrations at the peak of the orbital lightcurve and at the orbital minimum. Vertical dotted lines mark intervals of 118.2 s (the beat period), referenced to the 5 GHz data as in Fig. 9. Optical data from W1m are shown with an arbitrary flux scaling for comparison. In the bottom panel, we indicate the half-amplitude of the phase-folded and binned beat lightcurve in each orbital phase bin, at 1.5, 5 and 9 GHz.