Ham Radio General Class Practice Test

What type of device is often used to enable matching the transmitter output to an impedance other than 50 ohms?

1. Balanced modulator

2. SWR Bridge

3. Antenna coupler

4. Q Multiplier

The correct answer is: Antenna coupler

The correct answer is antenna coupler. An antenna coupler, also known as an antenna matching unit or tuner, is a device that matches the impedance of the transmitter to the impedance of the antenna system to improve the efficiency of power transfer and reduce signal reflections. Most transmitters, including those used in ham radio, are designed to deliver maximum power into a load that has a resistance of 50 ohms. When the antenna system has a different impedance, the antenna coupler adjusts this mismatch. Using an antenna coupler helps to ensure that the transmitter is operating effectively and that it delivers power to the antenna without significant reflections that can damage the transmitter or lead to poor performance. Through various configurations and adjustments, an antenna coupler can transform an antenna's impedance closer to the desired level, facilitating better communication. In contrast, a balanced modulator is used in the modulation process of signals and does not address impedance matching. An SWR bridge is useful for measuring the standing wave ratio, helping users ascertain the effectiveness of their antenna matching, but it does not perform the actual impedance transformation required to enable communication. A Q multiplier is a circuit used to enhance the selectivity of a radio receiver and is not related to antenna or transmitter impedance matching.