AP3340 again.
Radar altimeter - operates on a pulse system, measures height over a range in the order of 1,000 to 50,000 feet. Error in the absolute measurement is within +-100 feet, but changes of height at a constant level are measurable to within about +-30 feet.
Radio altimeter - operates on frequency modulation and covers the range from zero to about 5,000 feet. Error is proportional to height and may amount to +-3%.
However the AP dates from 1960 and todays manufacturers seem to use the terms radar and radio interchangeably.
Last edited by Brian Abraham; 25th Nov 2010 at 13:02.