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

To understand how mixing works in radio frequency (RF) systems, it's essential to grasp the role of the local oscillator. The local oscillator is an important component in superheterodyne receivers, where it generates a frequency that, when combined with the incoming RF signal, produces an intermediate frequency (IF).

By varying the frequency of the local oscillator, you can change the frequency of the signal being mixed. This mixing process takes place in a device called a mixer, which combines the RF input (the received signal) with the local oscillator frequency. As a result of this combination, two new frequencies are created: one at the sum of the two frequencies and one at the difference. The lower frequency, which is typically selected as the IF, is what gets processed further by the receiver.

This method allows receivers to efficiently process signals of different frequencies. By adjusting the local oscillator frequency, the receiver can tune into different RF signals while still processing them at a consistent intermediate frequency that is optimal for amplification and filtering.

The other inputs mentioned, such as audio input and demodulator output, do not play a role in frequency conversion to an IF in the same manner. The RF input is essential but does not vary; it is the local oscillator where the frequency adjustment