Single-pulse stacks of PSR B1822−09 from our data taken on 2023-04-24 showing several mode transitions. Each stack contains 56 min of data with a gap of 6 min between them for the phase calibrator scan. We applied a logarithmic greyscale mapping to bring out the faint emission in the IP and around the mode transitions. The vertical coloured lines delimit the two on-pulse phase regions, and the horizontal red lines on the right mark the rotations that were excised. The bottom panels show the normalised mean profile amplitudes A (black solid lines; left scale) and the phase-resolved modulation index m (black error bars; right scale).