Ham Radio Extra Class Practice Test 2025 - Free Extra Class License Exam Questions and Study Guide

Direct Frequency Shift Keying (FSK) involves applying the data signal directly to the transmitter's Variable Frequency Oscillator (VFO). This means that the actual frequency of the RF carrier is altered in direct response to the data being transmitted. As a result, the modulated signal remains clean and doesn't introduce additional distortion that can occur when other forms of modulation are used, allowing for more precise signaling.

In contrast, audio FSK typically modulates an audio tone that is then transmitted, rather than directly changing the carrier frequency itself. This method can define a cleaner signal processing approach; however, it tends to introduce additional complexity and can lead to potential distortion, depending on how the audio signal is handled in the transmission chain.

Understanding these differences is crucial for determining the best method of transmission in various circumstances, depending on the requirements of the communication system.