[Elecraft] Hearing CW - Fundamental Keying Waveform?

[Fred Jensen]

Darrell Bellerive wrote:
  > What is meant by "the fundamental keying waveform"?

I've wondered that myself.  CW is made up of two separate periodic 
waveforms ... one is symmetric (the dits) and one is asymmetric (the 
dahs) and they occur in a more or less random sequence.  For a given 
sending speed, each has a fundamental frequency:  a dit is two elements 
in length, one on and one off.  A dah is four elements in length, three 
on and one off.  So, a string of dits is a square wave and the sidebands 
arise from the infinite series of sine wave harmonics, starting with the 
"dit rate" needed to construct a square wave.  Likewise for a string of 
dahs, although the dah asymmetry would require a different coefficients 
in the infinite series of sine wave harmonics.  I guess the dit and dah 
rates are low enough that some of those close in harmonics fall in a 
normal CW passband and we hear them.  Of course, if we really do key 
with square waves, everyone else gets to hear all the others :-)

Fred K6DGW
Auburn CA CM98lw