I need to set up to radios with high gain directional antennas to talk to each other within a relatively small distance. The radio in questions is a RADWIN 5000 jet. The max distance I can set them up is about 20 feet from each other. Each antenna has a gain of 20dBi and the lowest power the radios will transmit at is -1dBm. So without attenuation each radio will receive a signal about 1/2W and we have a concern this will damage the receiver. Traditionally we could use a wave guide filter to attenuate the signal before the antenna but since this device is an all in 1 package (radio and antenna in one case) we don't have this option.
So my questions is this: does anyone have any suggestions on type of materials or sets ups I can put between the 2 devices to attenuate a 5GHz signal by say 30dBm?