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Topband: Key clicks

To: <topband@contesting.com>
Subject: Topband: Key clicks
From: w8ji at contesting.com (Tom Rauch)
Date: Sun May 11 17:40:34 2003
The spectrum of a OOK (CW) signal at 3 wpm is different from the spectrum at
> 30 wpm, so what does the last phrase in your response mean? The signals
will
> have energy content at (carrier rate +/- symbol rate), so the 30 wpm
signal
> would qualify as "more bandwidth" in my book.

Bandwidth is set entirely by the rise and fall time and shape of the rise
and fall of the signal. My keyclicks web page explains this, and has a link
to another analysis by W9CF.

http://www.w8ji.com/keyclicks.htm

If you have a energy storage system (like a narrow bandwidth multiple sweep
spectrum analyzer) that looks at frequency distribution in the time domain
over a period of many makes-and-breaks, "sidebands" will show as multiple
peaks and valleys that move around with frequency, but all of that energy is
contained in the same ultimate bandwidth as a single dot or dash and has the
same overall slope with frequency (bandwidth).

The"peaks and valleys" have nothing to do with what a  communications
receiver or the human ear receives, since neither the ear nor the receiver
can "store" sideband energy over multiple makes-and-breaks. One single click
that occurs once a year has all the bandwidth of a click that repeats 100
times a minute when it comes from the same envelope rise or fall.

73 Tom

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