Re: K3: killing RX key clicks

Posted by GW0ETF on Dec 02, 2009; 9:05am
URL: http://elecraft.85.s1.nabble.com/K3-killing-RX-key-clicks-tp4093607p4098722.html

My take is that in the extreme cw is an AM signal modulated by a pure square wave and as such prduces infinite odd order harmonics which will appear as sidebands/clicks. Filtering reduces the extent of the sidebands and smooths the square wave shape particularly rise and fall times but you will still have sidebands equivalent to 7th or 9th harmonics..? This would represent the ideal and you would have to be very close to the signal to hear the sideband energy - a bit of work on the calculator will tell you where the 7th or 9th harmonics would appear for a string of dits depending on the keying speed etc.

But I'm convinced that most bad clicks are actually a result of spurious switching spikes at the 'corners', often at the trailing edge and can produce sideband energy *way* out from the fundamental. This is nothing to do with the inherent physics of the cw signal and as such is curable.

73,

Stewart Rolfe, GW0ETF

Ron D'Eau Claire wrote

It's basic physics, Jim. A keyed signal is amplitude modulated and an
amplitude modulated signal produces sidebands.

......................

On CW those sidebands sound like clicks.

Ron AC7AC