Hi, I was reading about anechoic chambers for performing tests of RF equipment, and read that they are usually screened rooms, built as a Faradays cage (Grounded, closed metal structure) in order to block radiation from the outside, and stop radiation escaping. But also they coat the inside of the chamber with rubberised pyramidal structures of Radiation Absorbing Material (RAM) in order to absorb radiation emitted by the equipment, and reduce/eliminate reflections/echoes. What I was wondering is if the room is a faradays cage, then why use the pyramidal RAM structure to line the walls? Wouldn't a faradys cage just absorb all the radation, and route it to ground anyway? (And be cheaper and easier to build)?