What does a dummy load consist of?

A dummy load is used to safely test a transmitter without radiating a signal over the air. It achieves this by taking the RF power generated by the transmitter and dissipating it entirely as heat. To prevent any power from reflecting back to the transmitter, the dummy load must perfectly match the transmitter's expected impedance (usually 50 ohms). It uses a non-inductive resistor because any inductance would introduce reactance, which alters the impedance and creates unwanted standing waves. The resistor must be mounted on a heat sink to safely absorb and dissipate the continuous thermal energy. You should avoid the "50-ohm reactance" distractor, as a proper dummy load must be purely resistive, not reactive.