Question
What is indicated on a waterfall display by one or more vertical lines on either side of a data mode or RTTY signal?
Answer Options
- A) Long path propagation
- B) Backscatter propagation
- C) Insufficient modulation
- D) Overmodulation
Correct Answer: D
Explanation
A waterfall display visually shows the strength and frequency of signals over time. A clean digital signal, such as RTTY, should appear as two narrow, distinct lines (mark and space frequencies).
Overmodulation (or excessive drive) of the transmitter causes non-linear clipping, which generates spurious sidebands that spread out in frequency. On a waterfall display, these spurious signals appear as one or more vertical lines on either side of the data mode or RTTY signal, sometimes referred to as ‘splatter.’ This indicates that the transmitter’s audio or drive level is set too high.
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