Posted by P.B. Christensen on Jan 17, 2011; 6:39pm URL: http://elecraft.85.s1.nabble.com/K3-CW-transmit-filter-bandwith-tp5932777p5932829.html
> I am wondering why a narrow filter can cause key clicks?
One cause is related to the placement of the CW frequency in relation to the
filter passband. If skewed to the edge of a sharp filter, a severely
distorted waveform will develop. A CW waveform is a quasi square wave and
replication accuracy is dependent on a linear-phase response.