Where is the standard ariel ?
The only one I can see is on the left A post.
Ahhh... Picture tells 1000 words etc.
You have a mushroom roof, which started lif as a tintop, so the aerial arrangement is different. On a AFT, the aerial is above the back edge of the driver's door. I guess that the aerial you have on the passenger side A post is a standard tintop aerial. I'd have guessed that they would have been driver's side as well, but yours is passenger side.
Unless of course your Bongo started off as an AFT rather than a tintop before the mushroom roof was fitted? In which case the aerial could be fitted during the roof conversion and the passenger side makes sense to avoid it being in the way of the roof when opening it. If it was an AFT originally, you should have a roof switch in the headlining at the back of the cab (redundant), and a blanking plate where the original aerial was, above the driver's door.