What is the purpose of a dummy load when testing a radio transmitter?

• A. To increase output power
• B. To cool the transmitter
• C. To measure modulation quality
• D. To provide a known resistive load for calibrating output and preventing radiation during testing.

Answer: (D)

When you’re testing a transmitter, you want to know what the radio would do if it were connected to a real load, but you don’t want to actually radiate RF during bench work. A dummy load provides a known, primarily resistive termination (usually 50 ohms) that absorbs the transmitter’s RF energy as heat. This lets you calibrate and measure the output under controlled conditions without sending signals into the air, so reflections are minimized and the readings reflect the true transmitter performance. It’s rated for the transmitter’s power, so you can test safely without overloading the hardware. It doesn’t increase power, nor is its main job to cool the transmitter or to measure modulation quality—those require other equipment and setups.