I think what this boils down to is that I don't understand what an aerial is emitting. Is it a physical wave, where it transmits from the top of the aerial at one point in time, followed by transmitting a little further down at the next point in time, all the way through to transmitting from the bottom of the aerial, and then working its way back up, (i.e. like it's producing the shape of a wave over time T)
OR.... is it transmitting a signal in all directions at a particular strength, which gets stronger, until it's at its strongest (represented by the peak on the wave diagram) and then gets weaker until it's at its weakest (represented by the trough)?
OR... is it something different, or a combination of the above? Every page I look at seems to contradict the previous one I've just read.