Ham Amateur Radio Technician Practice Exam

What sound is heard from an audio device experiencing RF interference from a CW transmitter?

1. Chirping tones

2. On-and-off humming or clicking

3. Soft whispering

4. Steady tone

The correct answer is: On-and-off humming or clicking

When an audio device experiences RF interference from a Continuous Wave (CW) transmitter, the sound typically manifests as an on-and-off humming or clicking. This is due to the pulsed nature of CW transmissions, which consist of alternating signals of on and off that represent Morse code. As a result, when there is interference, it can create a rhythmic or intermittent sound in the audio device, leading to the characteristic on-and-off effect. This type of interference is particularly noticeable because CW signals are not steady—they abruptly transmit at specific intervals, which the audio device picks up and converts into audible noise. In contrast, sounds like chirping tones might suggest a more complex modulation rather than the straightforward on-and-off nature of CW. Soft whispering would imply a more continuous or static interference rather than pulsed, and a steady tone is less likely since CW is designed to transmit in a disjointed manner where the signal is either present or absent. Thus, the on-and-off humming or clicking serves as the most accurate representation of RF interference from a CW transmitter.