Ham Amateur Radio Technician Practice Exam 2026 - Free Technician Practice Questions and Study Guide

The frequency deviation in a frequency modulation (FM) signal refers to how much the frequency of the carrier wave varies from its resting value in response to the modulating signal. In this context, the deviation is influenced by both the modulation frequency and the characteristics of the modulating signal.

To determine the frequency deviation, we need to understand that a reactance modulated oscillator can produce frequency deviations that correlate with the modulating signal. Reactance modulation typically leads to variations in the oscillator frequency based on the instantaneous value of the input signal.

In this case, a 12.21 MHz carrier frequency modulated with a deviation of 5 kHz suggests that the oscillator can deviate 5 kHz above and below the carrier frequency. The frequency deviation can be calculated based on the modulation index (which directly relates to the deviation), but for this question, we focus on how the deviant oscillation connects to the total frequency involved.

Given the options, the value of 416.7 Hz arises as an appropriate approximation for the frequency deviation considering practical modulation practices in FM systems. It indicates how much the frequency of the oscillator shifts when subjected to modulation. This deviated frequency affords the transmitter's ability to convey voice signals while preventing interference with adjacent channels.