Its a very long time since I did my Radar maintenance course, ( and it wasn't RadAlt's) but... I thought Radar Altimeters were usually specified for low altitudes say less than 2,500ft. So if operating at 5000 or 10,000ft then isn't it possible you would see false echo's that would appear to be much closet than they actually are. First transmit pulse echo would appear in the quite time of the 2nd or 3rd transmit pulse and be interpreted as much closer distance ?
Hutch