[Elecraft] Bug Contact Bounce in CW+ Mode

[Don Wilhelm]

Paul and all,

We are discussing mechanical contacts that are "dry".

Contact bounce is a "fact of life" and is a problem to be contended with 
in any "dry" mechanical switch (bug, straight key, mechanical switch, 
relay, etc.)  It can be minimized with sealed mercury-wetted contacts, 
but without considering the mercuy wetted solution,  is a very real 
problem.  When designing a console for a large computer system, I added 
de-bouncing latches for every switch on the console panel because I knew 
that even high quality switches had contact bounce.  Fortunately, I was 
able to specify the switches to be SPDT so I could use set/reset latches 
for the de-bouncing mechanism.  Dirty contacts, dissimilar metals and 
other things of that nature only amplify the problem.  *All* switch 
contact closures will bounce - the question becomes "how long will the 
bounce condition be present".

There are effective de-bouncing circuits that can be used (set/reset 
latches if the switch is a SPDT), but the most common de-bouncing 
mechanism for SPST contacts is to sample the switch closure over a 
period of time (milliseconds), and if the closure exists during and 
after that time period, it is declared as a valid contact closure.

In the case of CW+, the timing must be smaller than the duration of the 
fastest allowable element (a dit time at 100 WPM - which may be just a 
"tick")., so yes, some contact bounce timings may be interpreted as 
valid dits (even though they may be shortened to "just a click" or a 
"tick").

IMHO, the CW+ option should not be used with bugs and straight keys 
because they suffer from potential contact bounce.  With logic 
controlled (and already de-bounced) circuits such as keyboard CW and 
other forms of computer generated CW, there should be no problem.

73,
Don W3FPR

Paul Christensen wrote:
>> "I think that is not being communicated here is, I'm NOT hearing 
>> "intermittent audible side-tone clicks" I'm here TICKS..."
>>     
>
> I am hearing the same "tick" on the leading edge of the side-tone only when 
> using a bug in CW+ mode.  It disappears when CW+ is deactivated.  So, 
> whatever we want to call it, an artifact is there, but I think it's 
> manageable external to the bug and K3.
>
> Paul, W9AC 
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>