ARRL Technician Practice Exam

Which of the following is used to convert a radio signal from one frequency to another?

1. Amplifier

2. Transponder

3. Mixer

4. Modulator

The correct answer is: Mixer

A mixer is an essential component in radio communication systems, specifically designed to convert a radio signal from one frequency to another. This process typically involves combining two different frequencies, resulting in new frequencies that are the sum and difference of the original frequencies. This capability is critical in various applications, such as frequency translation in superheterodyne receivers, where the incoming radio frequency signal is shifted to an intermediate frequency for easier processing. In contrast to a mixer, a modulator serves to encode information onto a carrier wave by varying its amplitude, frequency, or phase instead of changing the frequency of the signal itself. An amplifier boosts the power level of a signal but does not change its frequency. A transponder is designed to receive a signal and then retransmit it, typically on a different frequency, but it does not perform the mixing function like a mixer does. Thus, the mixer is the correct answer, as its primary function is to facilitate frequency conversion in radio systems.