I wrote:
>I recall an approximate estimate for keyed CW bandwidths is
about 4 times the keying speed.
Turns out that was from my memory from an FCC test
question years ago...and it is incorrect! The keyed bandwidth is
much more a function of the rise and fall times of signal waveforms,
as we're all too painfully aware of due to experience with certain
clicking radios being sold. Here are a couple of references about
keyed bandwidth:
"Spectral Analysis of a CW keying pulse" by W9CF
http://fermi.la.asu.edu/w9cf/articles/click/
"On the Occupied Bandwidth of CW Emissions" by KF6DX (TenTec)
http://www.doug-smith.net/cwbandwidth1.htm
Maybe the moral of this is to clean up your clicks if you
want to be heard well in very narrow filters! ;-)
73, Bill W4ZV
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