On my 2015 38RL, the antenna amp is to the left of the bedroom TV inside the cabinet and mounted under the top of the cabinet. When the amp is on (for antenna use) a small green LED illuminates, but is very hard to see.
2015 38RL with MORryde IS, residential fridge, DW, washer and dryer, generator, and slide in slide. 2 A/C, 1 HP and a fireplace. Added 17.5 inch wheels. Follows a 2013 Ram dually diesel with 8' bed and Reese 20K.