What is the primary purpose of a dummy load?

A dummy load is essentially a large resistor designed to safely absorb the output power of a transmitter without radiating it as an electromagnetic wave. Its primary purpose is to allow an operator to test or tune a transmitter without broadcasting a signal over the air. By connecting a dummy load instead of an antenna, you ensure that your testing does not cause interference to other stations on the band. The dummy load presents a perfect 50-ohm impedance to the radio, mimicking a perfectly tuned antenna, but converts the RF energy into heat instead of radio waves. The distractors are incorrect because a dummy load does not interact with modulation, nor does it improve actual antenna efficiency or receiver noise levels. It is purely a non-radiating substitute for an antenna during maintenance.