[Elecraft] [K3] CW transmit filter bandwith

[Paul Christensen]

> 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.

This topic was recently covered:

http://mailman.qth.net/pipermail/elecraft/2011-January/143163.html

Paul, W9AC