The spinal hump I was referring to Jaemz earlier is shaped like an elongated protrusion. I know what the average UHF aerial "bumps" look like, and this feature on the A300B4 does not look like one of those. To me, it looks like some kind of structure reinforcement for the top of the rear fuselage. To make it easier to translate what I mean, it looks like a long metal rod, about several meters long which is embedded in the rear third of the A300B4. This is funny to me because I thought everyone knew about this feature. This used to be how I would differentiate early A300s to the A310-200 (without the winglets). Just take a close look at some photographs, it really shouldn't be that hard to spot, it's like a long rod-like element on the top of the aircraft starting from the midpoint to the bottom of the tail. Good luck!