[Elecraft] K2 keying mod details and circuit theory

[Tom Hammond]

I can't tell you what the absolute max. speed with the mod in place it, but 
I've used it at 50WPM and the wavefirm still looks just fine and no keying 
problems whatsoever... looking at it on the monitor scope, I seriously 
doubt that 70 WPM will by problematic.

73,

Tom   N0SS   CFO #394 Cluck-cluck!

>I would like to ask what is the rated top speed for CW with the new mod?
>
>I am a CFO operator and am reluctant to give up my potential keying speed 
>of 70 WPM which I read "somewhere" was the rated top speed of the K2.  You 
>understand, I can't do that now, but I have "high hopes" for someday and 
>it's important to me to retain that feature and perhaps even extend it.
>
>If I may risk getting off topic and a bit controversial, it is my belief 
>that when the rise/fall times equal more than 1/4 of the dot length the CW 
>becomes harder to read, and when they equal 1/3 of the dot length an 
>expert is required.  Easiest code for novice users is 1/5 ratio, and below 
>this, no obvious improvement can be obtained.  I apologize if I'm 
>upsetting anyone with these three statements, but they are my belief.
>
>Next, I'll risk ire by saying that the rise/fall time can be a pure "S" 
>sinusoidal wave having minimum bandwidth, and this is most desirable, but 
>if it is not, the benefits of rapid rise/fall time still apply to the 1/5, 
>1/4, and 1/3 ratio mentioned in the paragraphs above.
>
>I have quite a few CFO friends who love the K2 for it's beautiful and 
>rapid keying!
>
>Please tell me this mod doesn't reduce the K2's potential speed.
>
>Thanks!
>
>TR WB6TMY
>K2/100/KAT100 S/N 0838
>
>At 10:56 AM 2/21/2004 -0800, you wrote:
>
>>The complete keying mod document will be posted next week. But here's the
>>executive summary: The original classic R/C exponential keying envelope is
>>converted to an optimized sigmoidal (S-shaped) envelope. This is done by
>>reconfiguring U10A as a 2-pole filer whose step response has the desired
>>rise/fall characteristics. But we were also careful to not make the rise and
>>fall times too long, which could result in "soft" keying. (We plan to 
>>write an
>>application note for those who want to custom-tailor the rise and fall times,
>>putting them somewhere in between the original and new values. Only one 
>>or two
>>component will need to be changed to achieve this.)
>>
>>73,
>>Wayne
>>N6KR
>
>
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