EGPWS
ChristiaanJ
...now I don't claim to be an engineer so correct me if I'm wrong. To my understanding the EGPWS uses an internal database of terrain in combination with a GPS position and therefore does not radiate. Basic GPWS (that modern aircraft still have in addition to the EGPWS), like you say, uses the radio altimeters. The difference is that we're sitting closer to the radar than the rad alt antenna - depending of aircraft type of course.
If you say that there's no radiation on the backside of the antenna and that the nose cone doesn't reflect any radiation back in our direction I suppose I'll just have to take your word - even if it sounds quite unlikely to me.
SAN