> Both the VI and VI+ reports show risetimes in the 2.0 - 2.5 ms range.
> According to the QST reviews, both make statements to the effect that
> this is "exceptional" or "excellent" keying waveshape. Perhaps the
> understanding of what is exceptional has changed because I note that Tom
> Rauch, W8JI is saying 4-5 ms is considered the correct risetime.
Correct to the extent that CW bandwidth may be minimized. I don't
necessarily agree with Tom's view that the "correct" CW waveform is one in
which the transmitted bandwidth is minimized by extending the rise and decay
of the envelope and turning the wave edges into a sine-slope characteristic.
The problem with Tom's approach is that in minimum signal conditions and at
relatively high CW speeds, his preferred wave form becomes difficult read.
In essence, the "correct" CW wave form is purely subjective.
My preference is for a fast leading edhe in the order of 1.5 mS, and a
trailing decay in the order of 5-6 mS, much the same as is often shown in
the older ARRL handbooks when grid-block keying is used. This produces a
percussive CW note with a slight "bell-sound." No, it is not as spectrally
pure as what Tom suggests, but the note is very distinctive and easy to
copy. A bit of extra bandwidth can sometimes be a good thing.
-Paul, W9AC
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