RWR relative vertical - how sensitive is it?

[VC]

If I understand correctly, the Russian RWR has two semicircles in the middle. If only the top one is lit, the radar is above you. If only the lower one, it's below you. If both, it's (approximately) co-alt.

 

 

I was flying 1v1 F-pole practice with some guys in the squadron, and I basically always had both semicircles lit, even when one guy dived hard and was coming in below my radar search cone. I would have slewed it down and found him, but I trusted the RWR telling me he was co-alt and just assumed he was notching or too far away to pick up.

 

 

My question is, at what relative angle does the RWR stop lighting both semicircles and actually start telling you the emitter is "above" or "below"? I would have thought "low enough to not be in my cone" would be a given but seems not.