Why Key Clicks?

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Why Key Clicks?

Post by KirtB » Thu Jul 27, 2017 5:11 pm

Why Key Clicks?, October 1966 QST

Waveform shaping is essential in today's crowded communications spectrum. Spectral masks are precisely defined in order to prevent "spreading" beyond the allocated frequency ranges at defined power levels. Whenever anything other than a continuous sinewave is being broadcast, there is spectral content generated in addition to the fundamental frequency. A Fourier transform of the waveform reveals which frequencies at what power levels comprise the waveform. The CW (continuous wave) signal used by Morse code operators is a pure sinewave (or nearly so), but there is a spectral problem with it every time the signal turns on or off because of the square-ish edges involved during switching. RC networks are used in the transmitter circuits to tame the edges so that they do not turn on and off so quickly and in doing so reduce the extraneous frequency content. Author George Grammer argues that even though the signal could theoretically be made 'clickless' (aka "chirpless'), there is an auditory benefit to the clicks or chirps that aids operators listening to high speed code transmissions. http://www.rfcafe.com/references/qst/why-key-clicks-october-1966-qst.htm
Kirt Blattenberger

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