Sennheiser AC 3200-II Active 8:1 Transmitter Combiner

Stack eight IEM transmitters in a rack and give each one its own whip and you have built an intermodulation generator. The AC 3200-II is the fix: eight RF inputs combined into a single antenna feed across 500 to 870 MHz, with the isolation between ports that keeps the transmitters from mixing in each other's output stages.

It handles up to 100 mW per channel and the inputs are protected to 250 mW, so it takes the high-power settings a touring monitor rig actually runs. Distribution attenuation is 0 dB plus or minus 1 dB, meaning what goes in comes back out. The unit is a 1U 19 inch chassis, 436 x 215 x 44 mm and roughly 4 kg, and it needs the NT 12-125D 12 V supply. A High Gain variant of the same chassis adds 3 dB.