Ham Amateur Radio Technician Practice Exam 2026 – The Complete All-in-One Guide to Exam Success

In a waterfall display, one or more vertical lines appearing on either side of a data mode or RTTY (Radioteletype) signal typically indicate overmodulation. Overmodulation occurs when the input signal level exceeds the defined limits of the modulation system, causing distortion in the transmitted signal.

The presence of vertical lines suggests that the signal's modulation is not clean, leading to splatter or excessive sidebands that create additional spikes in the frequency representation on the display. This manifests visually as vertical lines, which can indicate that the signal is being transmitted with too much power or improperly adjusted modulator settings, resulting in interference with adjacent frequencies. Understanding overmodulation is critical for optimizing signal clarity and ensuring effective communication without causing interference to other operators.