pg. 152 says this about the RKL - 41 :
"The RKL-41 is enabled by the BATTERY, 115V INVERTOR I, 115V INVERTOR II, and RDO CBs located on the main CB panel"
In-sim i can get reception on the RKL-41 with battery switch flipped on, but the ADF needle requires battery + only one inverter, and no need to flip the RDO CB switch.