-regardless of the type of HF Transceiver you are still transmiting a lot of RF energy.
Boeing 757/767 manual states
DO NOT OPERATE THE HF COMMUNICATIONS SYSTEM WHILE PERSONS REFUEL OR DEFUEL THE AIRPLANE. AN EXPLOSION CAN CAUSE INJURIES TO PERSONS AND DAMAGE TO THE AIRPLANE.
MAKE SURE PERSONNEL STAY A MINIMUM OF 6 FEET AWAY FROM THE VERTICAL STABILIZER WHEN THE HF SYSTEM TRANSMITS. RF ENERGY FROM THE HF COMMUNICATION ANTENNA CAN CAUSE INJURIES TO PERSONNEL.