The sideband could be all of the "random" dots that don't appear connected to the main three rectangular panels (now obscured by the cyclone). Imagine the sideband of a highly focused laser, the fringe of it's cylindrical surface, put through a lens the distortion could become immense. The result would a sideband that was splayed across a greater area.

Well yeah. Obviously wikipedia that shit. :) The problem is that most results discussing sidebands are referring to audio. While I have no doubt it is related to what we are doing, I think we're going to need to go a bit further into it than that.