The Spark Era: When Transmitters Roared For fifteen years wireless had one voice: the spark. This guide explains damped waves, why every spark station interfered with every other, and the long campaign to replace the crackle with a pure note. Quick facts Signal type damped waves Sound harsh crackle Range trick bigger sparks Improvement rotary gaps Verdict banned by treaty Spark's crudity forced the era's virtues - sharp operators and patient listening - while the industry hunted for continuous waves. Hearing a spark recording today explains twenty years of invention in a single burst of noise. Free tool and guides: Morse Code Works Morse Code Works - free Morse code tools and guides. Reference chart