What is the most common method of reducing key clicks?

To prevent the generation of key clicks on a CW signal, the abrupt on/off transitions of the transmitter must be softened. This is achieved by rounding the edges of the keying envelope, which requires making the transition take a fraction of a second longer—in other words, increasing the rise and fall times of the waveform. A common mistake is assuming that an RF low-pass filter at the transmitter output will fix the issue. Low-pass filters are used to suppress harmonic emissions (multiples of the operating frequency), whereas key clicks produce broadband noise immediately adjacent to the fundamental operating frequency, requiring shaping at the keying circuit.